{"product_id":"hella-h21w-24v-21w-halogen-bulb-bay9s-clear","title":"Hella H21W 24V 21W Halogen Bulb, BAY9S Clear","description":"\u003cp class=\"nvn-hero\"\u003eThe Hella H21W is a 21-watt halogen signal bulb for 24-volt systems, with a BAY9S bayonet base and clear glass that throws a crisp white light. It's the straight replacement for daytime running lights, position lamps, fog lights, and reverse lamps on heavy trucks, buses, and commercial equipment.\u003c\/p\u003e\n\n\u003cdiv class=\"nvn-description\"\u003e\n\u003cp\u003eThe Hella H21W is a 21-watt halogen signal bulb built for 24-volt electrical systems. It runs a BAY9S bayonet base and a clear glass envelope, so it throws a crisp white light. If you've got a worn or burned-out H21W in a heavy truck, a bus, or a piece of commercial equipment, this is the straight replacement that gets the light working again.\u003c\/p\u003e\n\u003cp\u003eH21W bulbs live in the signal and position end of a lighting system, not the main headlight. You'll find them doing daytime running lights, front position and parking lamps, fog lights, reverse lamps, and side markers. The clear glass means white output, which is exactly what those white-light roles call for. It isn't an amber turn-signal bulb and it isn't a headlight. Think of it as the dependable little bulb that handles the jobs around the edges of the lighting system.\u003c\/p\u003e\n\u003cp\u003eThe 24-volt rating matters. A lot of these bulbs go into heavy-duty and commercial gear, trucks, buses, agricultural rigs, and industrial equipment that run 24-volt systems instead of the 12 volts you'd see in a car. Match the voltage. A 24-volt bulb on a 12-volt circuit glows dim and weak, and a 12-volt bulb on a 24-volt circuit burns out fast. Check what your machine runs before you order.\u003c\/p\u003e\n\u003cp\u003eAt 21 watts on 24 volts, this bulb pulls right around 0.875 amp. That's an easy load on the wiring and the switchgear, which is part of why halogen signal bulbs have stayed in service so long. They're simple, cheap to replace, and they just work. Hella builds this one as part of their standard halogen line, made to original-equipment quality so the fit and the output match what rolled off the line.\u003c\/p\u003e\n\u003cp\u003eThe H21W name is a standard bulb designation, so it tells you what you're getting at a glance. H21W means a 21-watt bulb on the BAY9S base in a compact tubular glass envelope. That compact shape is why it fits the small reflector housings used for position and signal lamps, where there isn't room for a big bulb. Halogen keeps the output steady and the color honest across the life of the bulb, with no warm-up lag and no color drift as it ages.\u003c\/p\u003e\n\u003cp\u003eThe BAY9S base is a bayonet fitting with offset pins. The two locating pins sit at different heights, so the bulb only drops into the socket one way. Push it in, give it a small twist, and it locks. That keying is handy because it stops you from seating the bulb wrong. If your socket is a BAY9S H21W holder, this bulb fits it.\u003c\/p\u003e\n\u003cp\u003eInstall is quick. Kill the power first. Pull the old bulb with a gentle push-and-twist, line up the offset pins on the new one, seat it, and twist to lock. One tip worth following. Don't touch the glass with bare fingers. The oil from your skin bakes onto hot halogen glass and shortens the bulb's life. If you do touch it, wipe it down with a little rubbing alcohol before you power up.\u003c\/p\u003e\n\u003cp\u003eThis one ships as a single bulb. Most signal and position lamps work in pairs on a vehicle, left and right, so if one side has gone it's often smart to replace both at the same time. Grab two and you'll have a matched set with even output. Keeping a spare in the glovebox or the toolbox isn't a bad idea either, because a signal or position lamp that's out can mean a failed inspection.\u003c\/p\u003e\n\u003cp\u003eWe're an authorized Hella dealer, so every bulb is the genuine article with the full manufacturer warranty behind it. If you aren't sure whether your fixture takes an H21W on a 24-volt system, send us the make and model of your truck or equipment and we'll help you confirm it before you buy.\u003c\/p\u003e\n\u003c\/div\u003e\n\n\u003ch2\u003eKey Features\u003c\/h2\u003e\n\u003cul class=\"nvn-features\"\u003e\n  \u003cli\u003e21-watt halogen output on 24-volt systems for steady, consistent signal and position lighting\u003c\/li\u003e\n  \u003cli\u003eBAY9S bayonet base with offset pins indexes one way and drops straight into H21W sockets\u003c\/li\u003e\n  \u003cli\u003eClear glass puts out white light, right for DRL, position, fog, and reverse roles\u003c\/li\u003e\n  \u003cli\u003eDraws about 0.875 amp at 24 volts, an easy load on wiring and switchgear\u003c\/li\u003e\n  \u003cli\u003ePart of Hella's standard halogen line, built to original-equipment quality\u003c\/li\u003e\n  \u003cli\u003eCompact tubular glass envelope fits small signal and position housings\u003c\/li\u003e\n  \u003cli\u003eSold as a single bulb so you replace only what you need\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003cdiv class=\"nvn-trust\"\u003e\n  \u003ch2\u003eWhy Buy from NVN Marine\u003c\/h2\u003e\n  \u003cul\u003e\n    \u003cli\u003eAuthorized Hella Marine reseller, full manufacturer warranty\u003c\/li\u003e\n    \u003cli\u003eNMEA member and ABYC certified, advice from real boat techs\u003c\/li\u003e\n    \u003cli\u003eSame-day shipping before 3 PM ET on in-stock items\u003c\/li\u003e\n    \u003cli\u003eNY headquarters and Fort Lauderdale flagship retail store\u003c\/li\u003e\n  \u003c\/ul\u003e\n\u003c\/div\u003e\n\n\u003ch2\u003eFrequently Asked Questions\u003c\/h2\u003e\n\u003cdiv class=\"nvn-faq\"\u003e\n  \u003cdetails\u003e\n    \u003csummary\u003eIs this a 12-volt or 24-volt bulb?\u003c\/summary\u003e\n    \u003cp\u003eIt's a 24-volt bulb rated at 21 watts. Run it on a 24-volt system, the kind you find on heavy trucks, buses, and commercial equipment. It isn't meant for a standard 12-volt car circuit.\u003c\/p\u003e\n  \u003c\/details\u003e\n  \u003cdetails\u003e\n    \u003csummary\u003eCan I use this 24-volt bulb on a 12-volt system?\u003c\/summary\u003e\n    \u003cp\u003eNo. On 12 volts a 24-volt bulb glows dim and weak because it's only getting half the voltage it needs. Match the bulb to your system voltage and use a 24V bulb only on 24V circuits.\u003c\/p\u003e\n  \u003c\/details\u003e\n  \u003cdetails\u003e\n    \u003csummary\u003eWhat base does the H21W use?\u003c\/summary\u003e\n    \u003cp\u003eA BAY9S bayonet base. The two locating pins sit at offset heights, so the bulb only seats one way. Push it in, give it a small twist, and it locks into the socket.\u003c\/p\u003e\n  \u003c\/details\u003e\n  \u003cdetails\u003e\n    \u003csummary\u003eIs the light white or amber?\u003c\/summary\u003e\n    \u003cp\u003eWhite. The glass is clear, so it throws a crisp white light. That makes it right for daytime running lights, position lamps, reverse lamps, and clear fog lights, not amber turn signals.\u003c\/p\u003e\n  \u003c\/details\u003e\n  \u003cdetails\u003e\n    \u003csummary\u003eWhat's an H21W bulb typically used for?\u003c\/summary\u003e\n    \u003cp\u003eSignal and position jobs rather than main headlights. Common roles are daytime running lights, front position and parking lamps, fog lights, reverse lamps, and side markers.\u003c\/p\u003e\n  \u003c\/details\u003e\n  \u003cdetails\u003e\n    \u003csummary\u003eDoes it come as a single bulb or a pair?\u003c\/summary\u003e\n    \u003cp\u003eA single bulb. Most of these lamps work in left-and-right pairs, so if one side is out it's often smart to replace both at once for even output. Order two if you want a matched set.\u003c\/p\u003e\n  \u003c\/details\u003e\n  \u003cdetails\u003e\n    \u003csummary\u003eHow much current does it draw?\u003c\/summary\u003e\n    \u003cp\u003eAbout 0.875 amp. That's 21 watts divided by 24 volts, an easy load that's gentle on the wiring and the switch.\u003c\/p\u003e\n  \u003c\/details\u003e\n  \u003cdetails\u003e\n    \u003csummary\u003eIs this halogen or LED?\u003c\/summary\u003e\n    \u003cp\u003eHalogen. It's a filament bulb, so the output stays steady and the color stays honest over the life of the bulb with no warm-up lag.\u003c\/p\u003e\n  \u003c\/details\u003e\n  \u003cdetails\u003e\n    \u003csummary\u003eHow should I handle the bulb during install?\u003c\/summary\u003e\n    \u003cp\u003eDon't touch the glass with bare fingers. Skin oil bakes onto hot halogen glass and shortens the bulb's life. Hold it by the base, and if you do touch the glass, wipe it with a little rubbing alcohol before powering up.\u003c\/p\u003e\n  \u003c\/details\u003e\n  \u003cdetails\u003e\n    \u003csummary\u003eWill this fit my vehicle?\u003c\/summary\u003e\n    \u003cp\u003eIf your fixture uses an H21W bulb on a BAY9S base and runs 24 volts, this is a direct replacement. If you aren't sure, send us the make and model of your truck or equipment and we'll help you confirm it.\u003c\/p\u003e\n  \u003c\/details\u003e\n\u003c\/div\u003e\n\n\u003ch2\u003eTechnical Specifications\u003c\/h2\u003e\n\u003ctable class=\"nvn-specs\"\u003e\n  \u003ctbody\u003e\n    \u003ctr\u003e\n\u003cth\u003eTitle\u003c\/th\u003e\n\u003ctd\u003eH21 Halogen, 21 Watt, 24 Volt, Clear, Single\u003c\/td\u003e\n\u003c\/tr\u003e\n    \u003ctr\u003e\n\u003cth\u003eBrand\u003c\/th\u003e\n\u003ctd\u003eHella\u003c\/td\u003e\n\u003c\/tr\u003e\n    \u003ctr\u003e\n\u003cth\u003eManufacturer Part Number\u003c\/th\u003e\n\u003ctd\u003eH21W 24V\u003c\/td\u003e\n\u003c\/tr\u003e\n    \u003ctr\u003e\n\u003cth\u003eUPC\u003c\/th\u003e\n\u003ctd\u003e760687160137\u003c\/td\u003e\n\u003c\/tr\u003e\n    \u003ctr\u003e\n\u003cth\u003eBulb Type\u003c\/th\u003e\n\u003ctd\u003eH21W\u003c\/td\u003e\n\u003c\/tr\u003e\n    \u003ctr\u003e\n\u003cth\u003eTechnology\u003c\/th\u003e\n\u003ctd\u003eHalogen\u003c\/td\u003e\n\u003c\/tr\u003e\n    \u003ctr\u003e\n\u003cth\u003eWattage\u003c\/th\u003e\n\u003ctd\u003e21 Watt\u003c\/td\u003e\n\u003c\/tr\u003e\n    \u003ctr\u003e\n\u003cth\u003eVoltage\u003c\/th\u003e\n\u003ctd\u003e24 Volt\u003c\/td\u003e\n\u003c\/tr\u003e\n    \u003ctr\u003e\n\u003cth\u003eBase\u003c\/th\u003e\n\u003ctd\u003eBAY9S\u003c\/td\u003e\n\u003c\/tr\u003e\n    \u003ctr\u003e\n\u003cth\u003eGlass Envelope\u003c\/th\u003e\n\u003ctd\u003eT (Tubular)\u003c\/td\u003e\n\u003c\/tr\u003e\n    \u003ctr\u003e\n\u003cth\u003eLens Color\u003c\/th\u003e\n\u003ctd\u003eClear\u003c\/td\u003e\n\u003c\/tr\u003e\n    \u003ctr\u003e\n\u003cth\u003eLight Color\u003c\/th\u003e\n\u003ctd\u003eWhite\u003c\/td\u003e\n\u003c\/tr\u003e\n    \u003ctr\u003e\n\u003cth\u003eCurrent Draw\u003c\/th\u003e\n\u003ctd\u003e0.875 A at 24V\u003c\/td\u003e\n\u003c\/tr\u003e\n    \u003ctr\u003e\n\u003cth\u003eQuantity\u003c\/th\u003e\n\u003ctd\u003eSingle (1 bulb)\u003c\/td\u003e\n\u003c\/tr\u003e\n  \u003c\/tbody\u003e\n\u003c\/table\u003e\n\n\u003cscript type=\"application\/ld+json\"\u003e\n{\n    \"@context\": \"https:\/\/schema.org\",\n    \"@type\": \"FAQPage\",\n    \"mainEntity\": [\n        {\n            \"@type\": \"Question\",\n            \"name\": \"Is this a 12-volt or 24-volt bulb?\",\n            \"acceptedAnswer\": {\n                \"@type\": \"Answer\",\n                \"text\": \"It's a 24-volt bulb rated at 21 watts. Run it on a 24-volt system, the kind you find on heavy trucks, buses, and commercial equipment. It isn't meant for a standard 12-volt car circuit.\"\n            }\n        },\n        {\n            \"@type\": \"Question\",\n            \"name\": \"Can I use this 24-volt bulb on a 12-volt system?\",\n            \"acceptedAnswer\": {\n                \"@type\": \"Answer\",\n                \"text\": \"No. On 12 volts a 24-volt bulb glows dim and weak because it's only getting half the voltage it needs. Match the bulb to your system voltage and use a 24V bulb only on 24V circuits.\"\n            }\n        },\n        {\n            \"@type\": \"Question\",\n            \"name\": \"What base does the H21W use?\",\n            \"acceptedAnswer\": {\n                \"@type\": \"Answer\",\n                \"text\": \"A BAY9S bayonet base. The two locating pins sit at offset heights, so the bulb only seats one way. Push it in, give it a small twist, and it locks into the socket.\"\n            }\n        },\n        {\n            \"@type\": \"Question\",\n            \"name\": \"Is the light white or amber?\",\n            \"acceptedAnswer\": {\n                \"@type\": \"Answer\",\n                \"text\": \"White. The glass is clear, so it throws a crisp white light. That makes it right for daytime running lights, position lamps, reverse lamps, and clear fog lights, not amber turn signals.\"\n            }\n        },\n        {\n            \"@type\": \"Question\",\n            \"name\": \"What's an H21W bulb typically used for?\",\n            \"acceptedAnswer\": {\n                \"@type\": \"Answer\",\n                \"text\": \"Signal and position jobs rather than main headlights. Common roles are daytime running lights, front position and parking lamps, fog lights, reverse lamps, and side markers.\"\n            }\n        },\n        {\n            \"@type\": \"Question\",\n            \"name\": \"Does it come as a single bulb or a pair?\",\n            \"acceptedAnswer\": {\n                \"@type\": \"Answer\",\n                \"text\": \"A single bulb. Most of these lamps work in left-and-right pairs, so if one side is out it's often smart to replace both at once for even output. Order two if you want a matched set.\"\n            }\n        },\n        {\n            \"@type\": \"Question\",\n            \"name\": \"How much current does it draw?\",\n            \"acceptedAnswer\": {\n                \"@type\": \"Answer\",\n                \"text\": \"About 0.875 amp. That's 21 watts divided by 24 volts, an easy load that's gentle on the wiring and the switch.\"\n            }\n        },\n        {\n            \"@type\": \"Question\",\n            \"name\": \"Is this halogen or LED?\",\n            \"acceptedAnswer\": {\n                \"@type\": \"Answer\",\n                \"text\": \"Halogen. It's a filament bulb, so the output stays steady and the color stays honest over the life of the bulb with no warm-up lag.\"\n            }\n        },\n        {\n            \"@type\": \"Question\",\n            \"name\": \"How should I handle the bulb during install?\",\n            \"acceptedAnswer\": {\n                \"@type\": \"Answer\",\n                \"text\": \"Don't touch the glass with bare fingers. Skin oil bakes onto hot halogen glass and shortens the bulb's life. Hold it by the base, and if you do touch the glass, wipe it with a little rubbing alcohol before powering up.\"\n            }\n        },\n        {\n            \"@type\": \"Question\",\n            \"name\": \"Will this fit my vehicle?\",\n            \"acceptedAnswer\": {\n                \"@type\": \"Answer\",\n                \"text\": \"If your fixture uses an H21W bulb on a BAY9S base and runs 24 volts, this is a direct replacement. If you aren't sure, send us the make and model of your truck or equipment and we'll help you confirm it.\"\n            }\n        }\n    ]\n}\n\u003c\/script\u003e\n","brand":"Hella","offers":[{"title":"Default Title","offer_id":67598999781469,"sku":"2011375","price":8.29,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0299\/7266\/0317\/files\/ImageServerAPI_bc9825d8-c164-4c22-a246-50dc91dac99e.jpg?v=1790954090","url":"https:\/\/nvnmarine.com\/products\/hella-h21w-24v-21w-halogen-bulb-bay9s-clear","provider":"NVN Marine","version":"1.0","type":"link"}