<p>This caps is purposed for lenses with so-called OCT-19 mount (for 35mm fiml movie cameras Konvas-2M and Kinor-35). They made of firm ABS plastic. Weight is about 20gr. The cap has lugs to catch the lens mount's leaves so it wouldn't drop off the lens when you carry it in a bag.</p> <p>This cap has low profile to fit modern versions of OCT-19 lenses with short part begind a flange. If you have older lenses with long rear part and external guiding rail, you need deep rubber cap then.</p>