Kaifa 2pcs 4x6.35mm CNC Motor Jaw Shaft Coupler 4mm To 6.35mm Flexible Coupling OD 19x25mm Material: Aluminum alloy; Size: 25x19mm( L*D) Feature: Set screws (Coiling Clamping); Main Color: Silver tone The shaft couplers are widely applied to small CNC machines encoding and 3D printers Z shaft coupling, simplifies the debugging difficulty.