<p>This cap is made of very strong ABS plastic to protect mount and rear glass of your lens. It fits Arri-B (Bayonet) lens mount.</p> <p>The cap holds firmly on the lens mount due to catching lugs - it will not fall off accidentally. Just put it onto lens mount and turn it clockwise to lock it.</p> <p>Manufacturer and the cap type are indicated on inner bottom of the cap.</p> <p>Weight is 17 g.</p>