The optech usa lens support adapter is two strap adapters designed to help stabilize and support long lenses the adapters clamp to seams on a backpack or photo vest and then the circular section goes around the front of a long lens it will also work with many optech straps it has a quick disconnect that leaves the clamps in place and the straps on the lens this item is made in the usa stabilizes and supports long lenses clamps onto most backpack photo vests and optech st