Specifications:  Name: 7pcs Ball Screw Set.  Manufacturing Process: Rolled Thread.  Precision: C7 Grade.  Material: Carbon Steel.  Diameter: 12mm.  Pitch: 4mm.  Lead: 4mm.     Features:  ▲ FINE WORKMANSHIP:  This ball screw is with End machined. Diameter 12mm(0.36inch), Lead 4mm(0.12inch).  ▲ ADVANTAGE:  The ball screw is made of high-quality and durable CF54 steel that is wear-proof and resistant to high temperatures. It provides a helical raceway for ball bearings, which act as a precision screw, playing an essential role in situations where high precision is necessary.  ▲ MUTE OPERATION:  The ball screw kit features an accuracy grade of C7 with bearing fits less than 0.03 mm, making little noise while running.  ▲ WIDE APPLICATION:  The linear motion actuator is widely applied to CNC router, machine tools, robots, precision assembly equipment, etc.     Package Included:  1 x Ball Screw. 1 x Fixed Holder.  1 x BK10 End Support.  1 x BF10 End Support:  1 x Lock Nut.  1 x Circlip.  1 x 6.35*8mm Coupling