Gobo sizes: A, B, M and E

Updated 8 October 2026

A gobo's size letter tells you its outer diameter, which has to fit the holder, and its image area, the part that actually projects. Get the image area wrong and the edges of your design are cut off by the gate.

The common sizes

Figures are from Rosco's standard size table. ETC's pattern-size page agrees on A and B, and gives M as 65.5 mm with a 49.5 mm image. ETC's holder comparison lists larger image figures (78 mm for A, 68 mm for B), which appear to be the holder opening rather than the safe image area, so design to 75 and 64.5 mm. E is not one fixed size, which is why Rosco asks you to name the make and model.

Rosco also lists an S size (92 mm outer, 79 mm image, steel only) for ETC Source Four fixtures. Other makers use extra letters such as D, G, J and T; those come from individual makers' charts, so check with yours. Moving-light gobos are not standard sizes at all: they depend on the fixture and on which wheel the gobo sits in.

Which fixtures take which size

Always check the holder in your rig before ordering: many profiles accept more than one size with a different holder.

Leave a margin

Keep your design inside the image area with a small margin, because the edge of the image circle is where focus and brightness fall off first. Gobo Designer knows the gobo size and image area for 18 common profiles, keeps the artwork inside the image circle with a 1 mm margin, and warns when text leaves the beam.