YSTD&reg; 3pcs 1/4" 3/8" 1/2" Set Socket Bit Adapter Drill Power Extension Bar Hex Shank (Short) 1/4"*1/4"*50mm--1/4 "shank can be converted into 6.35 mm square 3/8"*1/4"*50mm--1/4 "shank can be converted into 9.53 mm square 1/2"*1/4"*50mm--1/4 "shank can be converted into 12.7 mm square Stainless Steel Locking Ball Ensures Secure Fit. Sockets Snap-On Tightly & Won't Slip Off 1/4-inch Hex Shank Prevents Stripping During High Speed Drill Operation