Patented bit holding system forces bit surface to opposing side for maximum bit retention Entry angle guides fastener Serration depth as deep as the fastener Large hard stamped identification KD Sockets use a Double Line (SAE) & Knurled Line (mm) to easily identify Standard vs. Metric Sockets Packaged in patented impact resistant Ã’slide rail system for easier positioning of sockets. Internal slides eliminate interference. Features Ball Bearing Retention Set Includes: 4, 5, 6, 7, 8, 9, 10, 12, 14, and 17mm Bit Sockets