Gobo Compatibility
Common letter sizes such as A, S, B, M and E each have an outer diameter (OD) and image area (IA). Those sizes are a useful starting point, but a gobo still has to match the specific fixture and holder.
Common gobo letter sizes
The table lists commonly used letter sizes. OD is outer diameter. IA is image area. Letter sizes are useful references, but the exact fixture and holder should be confirmed before ordering. A letter size is not a guarantee of fit.
| Size | OD | IA | Notes |
|---|---|---|---|
| A | 100 mm | 75 mm | Conventional ellipsoidals |
| S | 92 mm | 79 mm | ETC Source Four. Steel only. |
| B | 86 mm | 64.5 mm | Common ellipsoidal size |
| M | 66 mm | 48 mm | Junior ellipsoidals |
| E | 37.5 mm | 28 mm | Mini ellipsoidals. Confirm make and model. |
Moving-light wheels and architectural projectors are not a single letter size. Those fixtures need the make, model and, where relevant, the wheel.
37.5 mm gobos are used by many lighting fixtures, but compatibility depends on the specific fixture and holder design.
How to confirm compatibility
A letter size from the chart does not replace a fixture check. Send:
- Fixture model
- Existing gobo, if you have one
- Holder photo
- OD, IA or ID, and thickness, if already measured
- Gobo type
Then continue with gobo size, OD / ID, or replacement gobos. Request a quote for custom gobos.
FAQ
Is a letter size enough to order a gobo?
It is a useful starting point. Compatibility still depends on the fixture model, holder design, thickness and gobo type. Send the fixture model if you are unsure.
Is 37.5 mm a universal gobo size?
No. 37.5 mm is commonly listed as E size and is used by many mini ellipsoidals, but compatibility depends on the specific fixture and holder design.
What is the difference between OD and IA?
OD is the outer diameter of the gobo disc. IA is the image area, the region used for the artwork. IA is not the same as ID, and it is not automatically the projected image diameter.
Not sure which gobo size you need?
Send us your fixture make and model or a photo of your existing gobo and holder.