G10Q vs 2GX13: How to Tell Which Circline Bulb Base You Need
G10Q vs 2GX13: How to Tell Which Circline Bulb Base You Need
If you've ever pulled out an old circular fluorescent tube to replace it and found yourself staring at two pins wondering "is this a G10Q or a 2GX13?" — you're not alone. This is one of the most common mix-ups we hear about at NZ Lights, and it's an easy one to get wrong if you're not sure what to look for.
Why the confusion happens
Circline bulbs (round fluorescent tubes) come in a handful of different base/pin configurations, and manufacturers don't always make it obvious which one your fixture uses. Two bulbs can look almost identical in size and shape, but if the base doesn't match, it simply won't fit — or worse, it'll fit poorly and cause a bad connection.
The two most common bases you'll come across are:
G10Q — a 4-pin base, generally used on the more common household and office circline tubes (T9 and some T5 variants).
A G10Q T5 Circline 22W tube — notice the compact 4-pin base.
2GX13 — also a 4-pin base, but a different pin spacing and profile, typically used on larger, higher-wattage T5 circline tubes.
A 2GX13 T5 Circline 40W tube — a larger tube with wider pin spacing than G10Q.
How to tell them apart
The fastest way to check is to look at your old bulb, not the fixture — the base markings are usually printed right on the tube near the pins. If you can still read it, look for "G10Q" or "2GX13" stamped on the glass or the connector housing.
If the old bulb is broken or the markings have worn off, the pin spacing itself is the next best clue — G10Q pins sit closer together than 2GX13 pins. A rough way to check: measure the distance between the two pin pairs. If in doubt, the wattage can also be a hint, since 2GX13 is more commonly used on 40W-60W circline tubes, while G10Q covers a wider range including lower-wattage 20W-32W options.
Shop by base type
G10Q Circline options:
- G10Q T5 Circline 22W Cool White (190mm)
- G10Q T5 Circline 32W Warm White (270mm)
- G10Q T5 Circline 40W Cool White (320mm)
2GX13 Circline options:
Browse our full range in the Circline collection.
Still not sure?
Honestly, the safest option is to send us a photo of your old bulb (or its base markings) before ordering. We check these details for customers all the time, and it takes us two minutes to confirm the right match — much faster than guessing and having to send something back.
Need help identifying your replacement bulb? Get in touch with your lamp code or a photo, and we'll help you find the right one.
Also replacing a 2D lamp? See our Complete Guide to 2D Lamps in New Zealand — covering wattage, 2-pin vs 4-pin bases, and how to find the right replacement.
About NZ Lights
NZ Lights is a New Zealand-owned specialist lighting supplier with over 5 years of experience supplying replacement lamps for healthcare, dental, commercial, industrial and specialist applications.
From medical examination lights and dental equipment to specialist halogen, fluorescent and LED lamps, we help customers identify difficult-to-find replacements using model numbers, lamp specifications and equipment requirements.
Whether you're replacing a single bulb or sourcing lamps for a hospital, clinic, business or facility, our team is here to help you find the correct solution.
Need help identifying your lamp? Contact NZ Lights or send us a photo of your existing lamp, and we'll help you find the correct replacement.
