The set contains 6 socket adapters for reducing or increasing the square drive size. The F is the size of the female end and the M is the size of the male end.
Each item is made from high-quality Chromium Molybdenum Steel steel* 
These adapters are suitable for use with pneumatic air tools and cordless tools such as impact wrenches. Contains sizes: ¼”F x 3/8”M, 3/8”F x ¼”M, 3/8”F x ½”M, ½”F x 3/8”M, ½” F x ¾”M, ¾”F x ½”M