<p>This cap is made of firm ABS plastic. Weight is about 20gr. The cap has lugs to catch the lens mount lugs so it wouldn't drop off the lens when you carry it in a bag.</p> <p>These have 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, then you need deep rubber cap instead.</p>