Built on a framework of full, skeletonized stainless steel liners and a stout stainless steel back spacer, the Spyderco Efficient knife has handle construction that provides serious structural strength and forms the foundation of its sturdy Liner Lock mechanism. All Efficient knives proudly includes the high-performance features and benefits that savvy knife users have come to expect from Spyderco knives in a format that suits practically every budget. An index-finger choil (finger groove) at the base of the edge provides a comfortable forward grip, allowing enhanced control during precise cutting chores. The factory model number for the Efficient is Spyderco C216.