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 4mm, 5mm, and 6mm Slotted, #1, #2, #3 Phillips, and #2 POZIDRIV Bit Sockets7 Piece Screwdriver Bit Socket Set includes: 4mm, 5mm, and 6mm Slotted, #1, #2, #3 Phillips, and #2 POZIDRIV Bit Sockets packaged on a clip rail.