Clamp can be rotated 360 degrees, you can make the ear hook more close to the ears,feel more comfortable. These hooks are a universal type made to fit as many Bluetooth models as possible. Clamp with PC and ABS engineering materials, toughness super, not easily broken. User-friendly design, clamp with a telescopic function, according to the size of the ear to adjustment. Environmentally materials,prolonged use will not skin allergies,wear for a long time will not be painful. Specification: Clamp Material:PC and ABS Clamp Size - 0.20 (5mm) Diameter Post Suitable for Headset Clamps Size 5.0-5.8mm Clamp Size - 0.24 (6mm) Diameter Post Suitable for Headset Clamps Size 6.0-6.8mm Clamp Size - 0.28 (7mm) Diameter Post Suitable for Headset Clamps Size 7.0-7.8mm Clamp Size - 0.31 (8mm) Diameter Post Suitable for Headset Clamps Size 8.0-8.8mm Clamp Size - 0.35 (9mm) Diameter Post Suitable for Headset Clamps Size 9.0-9.8mm Clamp Size - 0.39 (10mm) Diameter Post Suitable for Headset Clamps Size 10.0-10.8mm Package Includes: 1 Piece Bluetooth Headset Hook Note: You must measure the size of clamp before you buy the good,avoiding the wrong size and cannot be used.