Phillips head machine screw 4 X 1/4 dia 20 TPI This is a phillips head machine screw with a length of 4 inches and diameter of 1/4 inches. The length is based on the actual screw length not including the head of the screw. The thread is UNC (Unified National Coarse) which is for this 1/4 inch screw is 20 TPI (Threads per inch).
