... 3. Brand name Electrical parts. Instructions for Electric-cable-screw.Hopper and double-alloy screw(screws,machine screw): 1.We ... include: Variable pitch and variable depth, variable pitch and equal depth, variable depth and equal pitch, and equal depth and pitch. Groove multi ... nitro alloy steel, applying the method of hardening and tempering and nitriding, thus it enjoys the characteristics of long ...