Drop-Forged, Heat Treated Carbon Steel. Oil-Quenched, Black-Oxide Finish for Durability. Spring-Loaded Ball Bearings Hold Sockets Securely. Hole on Reducers for Locking onto Drive Tang. Special designed for use with Air Tools. Impact Reducer Sizes- 3/8" (F) x 1/4" (M). 1/2" (F) x 3/8" (M). 3/4" (F) x 1/2" (M).