Screw Sizes: 1"x10g (25x4.77MM), 1.5"x10g (38x4.77MM), 2 "x10g (50x5MM) and 3 "x10g (75x5MM). This sale is for 1 to 300 screws. A double screw, the threads run in opposite directions, tightening, and pulling together when twisted.