Patented bit holding system forces bit surface to opposing side for maximum bit retention - strength. Packaged in patented impact resistant "slide rail" system . Heat treated socket bases for durability and service ability. Chrome sockets; S2 and alloy steel bits. Includes 8mm, 1/4", and 3/8" Bit Sockets 3 Piece 3/8" Drive SAE/Metric Hex Bit Socket Set includes: 8mm, 1/4" and 3/8" Bit Sockets packaged on a clip rail.