Farpoint Bahtinov Focus Mask — 55mm DSLR LensBahtinov focus mask for camera lenses with 55mm filter threads. Snaps into the threads of an inexpensive 55mm UV filter (one time install). From there, screw the filter onto your lens for a focus check, then unscrew it to shoot quick and tool free. Made in our own shop in the USA American materials, American machinery, by Americans. Works with any DSLR or mirrorless camera lens that takes a 55mm front filter. UV filter sold separately any inexpensive