How to Identify Halogen and Xenon Bi-Pin Bulbs

Halogen BiPin

So one of the bulbs in those little “puck” lights under your kitchen cabinets or the light in your desk lamp has burned out. You may have even had a burn-out with a landscape bullet light. Once you figure out how to get the fixture apart, you find a tiny bulb with two pins you don’t recognize. Now what?

Sure, you can throw the entire fixture out and just get a new one. That may be easier, but it definitely won’t be cheaper. What happens when the bulb burns out again (which it certainly will)? Are you going to just keep buying replacement fixtures?

Relax. We at 1000Bulbs.com have you covered. Identifying and replacing your existing bi-pin xenon bulb (sometimes called ‘2-pin bulbs’ or ‘T-bulbs’) is easier than you think. Just follow these five simple steps:

Step 1: Measure the Pin Spacing

How far apart are the pins from each other? You can figure this out by getting a ruler and measuring the space between the pins. The space between the pins is measured in millimeters. Write this measurement down as it will help you find the right base type.

Step 2: Determine the Bulb Voltage

Check the fixture housing or socket and see if there is a label that tells you the voltage of the original bulb. The label will most likely have a UL or CSA symbol. If it’s not on the fixture, try to find it on the bulb itself. When you find the voltage, write it down. If you can’t find the label or the label doesn’t list the voltage, don’t worry. You may still find the correct bulb with some tips coming up in step 4.

Step 3: Check the Pin Type

Now check the pins on your existing bulbs. Are they straight or looped? Most bi-pin bulbs will have straight pins, but there are also bi-pin bulbs that have looped pins. Knowing if the pins are straight or looped will help you to further narrow down your bulb selection. Along with your pin measurements and voltage, make sure to jot down if your pins are looped or straight.

Step 4: Find Your Bulb

Now that you’ve got the bulb spacing, pin type, and (hopefully) voltage, it’s time to find your bulb. If you measured 4 millimeters between pins, that means you have a G4 base bulb, which comes in 6, 12, or 24 volts. If your measurement is just a hair wider than 6 millimeters, you have a bulb with a G6.35 base, which comes in 12, 24, or 120 volts. A measurement of 8 millimeters means you have a G8 base xenon bulb, which only comes in 120 volts. Looped pins spaced 9 millimeters apart means you have a G9 base bulb, which also only comes in 120 volts.

Step 5: Install Your Bulb

After you’ve figured out what bulb you need, installing it is simple. Your fixture has a glass lens that fits over the bulb. After you remove the lens, insert the new bulb into the socket and replace the lens. Be careful not to touch the bulb itself, as the oils on your fingers will damage the bulb, shortening its life and maybe even causing it to melt. Some bulbs come with a wrapping around the bulb to prevent damage when installing them. If your bulb didn’t come with a wrapping, wear gloves or use something to wrap around the bulb, but be sure to remove the wrapping after you install the bulb.

That’s all there is to it. Remember, replacing your bulb is much cheaper than replacing the whole fixture. While replacing the bulb may not be as easy, after a few times, you’ll get the hang of it. If you have any questions about these bulbs or just questions in general, don’t be shy! Drop us a comment in the box below or reach out to us Facebook, Twitter, or Google Plus.

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Jordan Loa

Jordan is a copywriter at 1000Bulbs.com. Check back often for new entries in his "Light Post" series of happenings in the world of lighting.

  • http://n/a L. W. Still

    I need halogen 10 watt 12 volt g4, for outside lighting

    • Jordan Loa


      We thank you for reaching out to us! In order to recommend a bulb that fits your needs, we’ll need to know specifically what kind of bulb you’re looking for, such as base type, and what application it’ll be used for. Thanks!

  • http://www.stbartholomewchurch.org Deacon Bob Gurske

    I am just discovering your articles on lights and lighting. They’re so informative! As Director of Operations for my church I must keep up on changes in technology and EISA so that the building will continue to be properly lit in a comfortable and appropriate ambiance. Thank you, and please keep the information coming!

    • http://www.1000bulbs.com Courtney Silva

      Thanks for the kind words, Bob! We’re glad you’re finding our posts to be useful. Let us know if there’s anything else we can answer for you or help you with!

  • Frank McChristian

    Thanks for the information. The bi-pin Xenon bulb burned out in my desk lamp yesterday and I went to the hardware store to buy a new bulb. The bulb is 12V Type JC G6.35 base. I was not able to insert the new bulb into the lamp socket. Looking at the old bulb, I noticed that the pins were slightly shorter than those on the new newly purchased bulb. And the diameter of the pins was slightly wider on the new bulb. My lamp is over 20 years old. Is it possible that the old bulb is a type that is no longer manufactured? Please advise. Thanks so much!

    • http://www.1000bulbs.com Will Parsons

      It’s difficult to know without seeing the bulb itself, Frank, but you should be able to find out if you still have the original bulb. Pin and base types haven’t ended production since they’re only sizes. The base type should be listed on your old bulb, if it isn’t, measure the diameter of the pins as well as the distance between them. Or, just take the old bulb with you to compare against other bulb base types. If you’re missing the old bulb, try a search using the lamp part number to see if anyone has recorded information on what bulb type it uses. If that doesn’t solve it, feel free to call us up and we’ll help you find the proper replacement.

      • Frank McChristian

        Thanks for the info, Will. I’ll give your suggestions a try and see what I can find. If I have no luck, I’ll give you guys a call. Thanks!

  • JB

    I have some puck lights that use 20 watt halogen bulbs with a G8 base. I have been having trouble finding replacements. However, I have been able to find 20 watt xenon bulbs with G8 bases. Is it okay to replace the halogen bulbs with the equivalent xenon bulb?

    • http://www.1000bulbs.com Will Parsons

      Hi JB. The xenon bulbs should work just fine. I’d recommend testing the fit first with a single bulb, but there shouldn’t be any problem.

  • E

    Your picture is kind of misleading. While the bulb in the picture is a G9 it is NOT a bipin. Also, I understand putting the coin next to the bulb for size reference but I don’t recognize this coin – it’s not a penny so what is it?

    Your article is good but I’d do something about the picture if I were you :)

    • http://www.1000bulbs.com Will Parsons

      Nice catch E. I’ve updated the picture to an actual bipin. As for the coin, I’ve no idea what it was either.

  • livy

    How do I remove the burnt out 2 pronged bulb from my hanging lite fixture? It does not want to turn either way. Tx a lot for help

    • http://www.1000bulbs.com Will Parsons

      Not all mini bi-pins are twist and lock plugs. Try firmly pulling the bulb straight out of the socket. If needed, try gently rocking the bulb back and forth as you pull it free, but only slightly, to avoid breaking the pins.

  • Paul K.

    I just wanted to leave a quick thanks. This step-by-step guide taught me exactly what I needed. Thank you!