Aluminum alloy ring: CNC machine precision machining, hard anodized black UV filter with multi-layer coating. Yellow and orange filters use true optical glass lenses with 98% light transmission rate (not other cheap dyed films or plastic films, please distinguish). Rollei 35, 35 T, 35 TE B35, 35LED cameras use 24mm size. Rollei 35 S, 35 SE, 35Classic cameras use 30.5mm size