1. The lens collar is tailor-made and compatible with Tamron 18-400mm f/3.5-6.3 Di II VC HLD B028 Lens (for EF Mount, F Mount), can't be used for other lenses; reserved window for the LOCK switch on the lens, other switches are blocked; the lens collar is fixed by the switch and cannot be rotated. | 2. The net weight of the tripod mount ring is about 155g, carved into an irregular shape, the smallest diameter is about 76mm, the contact surface with the lens is made of 3M plastic film, the widest is about 18mm, and locked by the large non-slip knob. | 3. The tripod collar bottom is added 55mm long Arca fit quick release plate feature, can be used with 39mm Arca-swiss fit tripod ball head, panoramic head and clamp directly; more practical than lens collars without dovetail groove. | 4. The Lens support bottom reserved 1/4" and 3/8" screw holes and stainless-steel anti-slip screw for fixing lens to tripod directly. | 5. The tripod ring is made of Aviation Aluminum, CNC precisely machined, hollow-out weight reduction design, polished and surface anodized finish. The appearance and exquisite workmanship are much better than similar products made by mold.