PLEASE NOTE: The shaft coupler is not elastic, can not modify the concentricity.Shaft must be located in a straight line. If your equipment is eccentric already, then it will make noise and cause off-centering. Please be cautious before your final purchasing, thank you. Product Name: Shaft Plum Coupling Type: Plum Shaped Shaft Usage: 8mm to 10mm / 0.31inch to 0.39inch Size: :L30mm x D25mm/1.18inch x 0.98inch( L*D) Material: Aluminum Alloy,Polyurethane Main Color: Silver Tone,Red Weight: 29.4g x 2pcs The shaft couplers are mainly used for CNC machines,servo motors, spindle, step motor etc Package Content: 2 x Shaft Plum coupling 1x Allen Key