Note that the sizes are in 3mm increments. If you are right on the edge, get the larger size. We can make custom sizes for anything, just reach out to us.
It’s best if you measure the OD of your light bezel or optic objective using a micrometer. Alternatively, most manufacturers list measurements on their website. See below for common fitments:
Surefire Vampire Light Head - 25-28
Aimpoint T-1 (and similar, like PA and Sig dots) - 28-31
Modlite PLHV2 Light Head - 31-34
Surefire Turbo - 31-34
Modlite Multi-Mode OKW Light Heads - 31-34
Most LPVOs, like Trijicon Accupower 1-8 and Vortex HD 1-10 - 34-37