Absorption of parallel, angular misalignments and shaft end-play by spring action. Widely used in power systems for encoders, instrumentation, lead screws, small pumps, feed rollers and wherever a lightweight to medium duty, torsionally flexible coupling is required. Product Name : Beam Coupling; Features : Screw Type(Coiling Clamping) Shaft Usage : 8mm to 8mm / 0.31" to 0.31"(5/16" to 5/16"); Length : 25mm / 0.98" Diameter : 18mm / 0.71"; Material : Aluminum Alloy Color : Silver Tone Weight : 13g; Package Content : 1 x Beam Coupling Note:Light and varied displays can cause the colour of the item in the photo a little bit various from the genuine thing. The size allowed error is +/- 1-3cm.