781/5 Set 1Connection parts, 5 piece set For manual and machine operated tools (non impact), with ball stop groove, knurling at the rear end for manageability during manual use; chrome vanadium, brushed chrome plated finish 781 A: 1 4" socket square head drive, for 3 8" and 1 2" square head socket wrench inserts with ball lock; 781 B: 3 8" socket square head drive, for 1 4" and 1 2" square head socket wrench inserts with ball lock; 781 C: 1 2" socket square head