There is no markings, labels, or anything on the light bulb

House is in Los Angeles, built in 1942

Lightbulb is in a recessed light.

https://www.bulbs.com/learning/basechart.aspx I've looked at all the possibilities, but there are just too many I can't tell the difference. Does anybody have an idea of which base this is?

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  • I would imagine that measurements of the length and space between the two pins is needed. Comparing a picture with another picture without known measurements is useless. Taking the light to a light shop is probably the fastest way to know, especially if they have an old guy around who knows his stuff.
    – crip659
    Jun 10, 2023 at 22:25
  • that's a great idea, i will do that thanks @crip659!
    – A O
    Jun 10, 2023 at 22:51
  • If you replace with led, and there was an extra glass lens in the light fixture, remove the lens. (It was there to prevent hot shards of glass flying, and it can help overheat the led.) Jun 11, 2023 at 3:26
  • Yeah I'll definitely go with LED, thanks for the tip
    – A O
    Jun 11, 2023 at 16:00

2 Answers 2


It is an MR16 lamp (Multifaceted Reflector 16/8 inch), with a gu5.3 base (5.3mm spacing).

You might want to take a look at the Wikipedia page for ANSI designation for wattage and reflector angle designation. Wattage is significant because if the fixture only has a 50w supply a 75w lamp (EYF, EYC, EYJ) may damage the power supply. Small beam designs cause bright spots on close surfaces.

If replacing the lamp with standard halogen bulb be careful to not touch the bulb, oils from your hands can shorten lamp life.


It is an MR16 low voltage, halogen, 12 volt bulb. It probably was not installed when the house was built but later installed during a renovation. They come in a number of different wattages so it's important you get the right one. You might have to remove some of the other bulbs to see the writing on them. They are readily available at most home stores.

  • i pulled out two out of two (in bathroom) neither had writing :/ i will try taking it to a store to confirm, but thanks for leading me in the right direction!
    – A O
    Jun 10, 2023 at 22:52

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