Patented bit holding system forces bit surface to opposing side for maximum bit retention - strengthPackaged in patented impact resistant "slide rail" system Heat treated socket bases for durability and service abilityChrome sockets; S2 and alloy steel bitsIncludes 4mm, 5mm, and 6mm Slotted; #1, #2, #3 Phillips; and #2 POZIDRIVĀ® Bit Sockets7 Piece Screwdriver Bit Socket Set includes: 4mm, 5mm, and 6mm Slotted; #1, #2, #3 Phillips; and #2 POZIDRIVĀ® Bit Sockets packaged on a clip rail.