Square Drive Adapter are used as a converter to permit use of sockets with impact wrench of different drive sizes i.e. higher or lower. These are available in 1/4", 3/8", 1/2", 3/4", 1", 1 1/2" and 2 1/2" square drives of adjacent reducing / increasing combinations of male and female drives.
These are of two designs:
Square Drive Adaptor with 2 cross holes for conventional impact wrench.
Square Drive Adaptor with groove for locking ring and pin for impact wrenches with cross hole in male square drive.