SK 4941 3 Piece 3-Inch, 7-Inch, and 15-Inch Locking Extension Set 3-piece 1/4-inch drive locking extension set stands up to harsh working environments Patented SuperKrome finish for durability and maximum corrosion resistance SureGrip hex design holds socket on extension; prevents socket from getting stuck to fastener 4 recess detents in socket drive square for quick attachment 3-, 7-, and 15-inch locking extensions