Hi Everyone, So I'm thinking about adding to my gobo repertoire for my moving lights (NW Lighting FX fixtures) but I can't seem to figure out what size I would need to order for new gobos. Basically, the manual says " gobo size 21.8mm / 15 mm image." On the rosco website, it seems like there are seizes that are bigger and small than that, but nothing with those measurements. Should I go to the next smallest size (20 mm /13 mm)? Or is there a better way to tell? Thanks in advance!