These sockets have a built in swivel joint for impact applications. The swivel is a simple coupling device that allows the thing fastened to turn around freely upon it. It is a flexible sockets particularly useful for tightening nuts located at different angular positions. These are available in 3/8" & ½" square drives from 7 mm to 24 mm across flat & equivalent SAE sizes. The swivel sockets with built in extension are also available to cover reach up to 200 mm.