Engineered to maximize runtime. Thin kerf design for high efficiency. Carbide teeth for long life. Self-feed pilot bit for fast, efficient cutting. Spring loaded collar automatically engages drive pins to prevent hole saws from locking to the mandrel. Kit includes three hole saws 2-1/8, 2-9/16 and 3-5/8 in, one quick-change mandrel and three self-feed pilot bits.