Are GX24Q-3 bulbs compatible with G24Q-3 bases and vice versa? Can a GX24Q-3 bulb be safely powered by a G24Q-3 base? Can a G24Q-3 bulb be safely powered by a GX24Q-3 base?

EDIT: If not, then can a 26-watt GX24Q-3 CFL replace a same-watt G24Q-3 CFL in a G24Q-3 ballast? I have a G24Q-3 ballast that has always used 26-watt G24Q-3 CFL. When the last CFL died, I replaced it with, and was able to fit, a 26-watt GX24Q-3 CFL in the ballast. But I get only one flicker (and nothing else) each time when powering on, so is the GX24Q-3 bulb incompatible or just a bad bulb?

Adding to the confusion, this page markets an LED bulb that’s “Compatible with only base G24q-3/GX24q”. I didn’t use that LED; my test used a CFL of a different brand, which doesn’t indicate whether it’s compatible with G24Q-3 ballasts. This other site’s search filter consolidates G24Q-3 & GX24Q-3.

The notches of the G24Q-3 and GX24Q-3 bulbs are located at the same 1- and 7-o’clock positions. The bulbs are different in their bezel above the notched section: a hexagon bezel for GX24Q-3 bulb and a rounded square bezel for the G24Q-3 bulb. I now see from some answers’ diagrams that the G24Q-3 bulb has a longer central peg (a.k.a. stabilizing block) than the GX24Q-3 bulb. Because my G24Q-3 ballast’s socket is deep enough to fit the G24Q-3 bulb’s stabilizing block, the shorter block on the GX24Q-3 doesn’t cause any fit issues. The plastic holder section of my G24Q-3 ballast goes only up to the notched cross section of the G24Q-3 bulb, so the hexagonal bezel of the GX24Q-3 bulb doesn’t cause any fit issues either. Both G24Q-3 and GX24Q-3 bulbs can fit in a G24Q-3 ballast. If the socket on a GX24Q-3 ballast is only as deep as its own bulb type’s stabilizing block, then G24Q-3 bulbs can’t fit in GX24Q-3 ballasts. Is this length difference designed to make GX24Q-3 bulbs backwards-compatible with G24Q-3 ballasts and prevent G24Q-3 bulbs from being forwards-compatible with GX24Q-3 ballasts?

2 Answers 2


Are GX24Q-3 bulbs compatible with G24Q-3 bases and vice versa?


  • The GX24Q-3 base is designed for use with 4-pin triple-tube lamps.
  • The G24Q-3 base is designed for use with 4-pin double-tube lamps.

The electronics in the base (often referred to as the electronic ballast) is likely designed for the specific load configuration.

The IEC specifications for dimensions etc costs money and is copyrighted - so they are difficult to obtain casually. The G24 appears to have a longer/deeper central peg.

  • The first letter G indicates a multi-pin push-fit connector type?
  • The second letter, if present, X, is for triple-tube variants.
    For other types X can mean twist-lock as in GX53.
  • The number after that is the major pin spacing in mm (24mm).
  • The final letter indicates bi-pin (d) or quad-pin (q).
  • The final digit, indicates the power range ("-3" = 26W - 32W).

Useful references:

  • +1 for link, observing number of tubes, & power nomenclature. The shorter stabilizing block of the GX24Q-3 bulb doesn’t prevent it from fitting into the socket of the G24Q-3 ballast; only a longer block would. The notches line up. I used same-watt bulbs. Is my GX24 bulb incompatible or a bad bulb? I just edited the question to add more details.
    – CodeBricks
    Mar 30, 2018 at 4:52
  • 1
    @Codebricks: The physical connector may be compatible but the electronics might not be (a fancy way of saying I don't know - sorry) Mar 30, 2018 at 12:05
  • Thanks anyway. Your existing answer is still helpfully informative.
    – CodeBricks
    Mar 31, 2018 at 10:53

No. They are very different. Different shape, different pin spacing.

The picture below was shamelessly borrowed from this article.

socket drawings

  • Thanks but link doesn’t specify pin spacing. I’ve fit a GX24Q-3 bulb in G24Q-3 base. Notches are spaced the same. Only difference I saw was hexagon (instead of square) bezel above notched cross section. Holder goes only up to the notches, so fit wasn’t issue. Got only a flicker when power on, so don’t know if it’s incompatible or bad bulb. This page markets a bulb (I didn’t use this though) that’s “Compatible with only base G24q-3/GX24q”. This other site’s search filter consolidates G24Q-3 & GX24Q-3.
    – CodeBricks
    Mar 29, 2018 at 4:18
  • ...Addendum: the first link in my previous comment shows an LED bulb, but the bulb I tried was a CFL of a different brand. My base was manufactured before the time of consumer LED bulbs. I don't know if those differences render my comment's first link inapplicable to my issue.
    – CodeBricks
    Mar 29, 2018 at 4:25

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