IVY Classic 10973 1/4 to 1/2-Inch Router Collet Adapter, 1/Pouch Adapts router bit with 1/4-inch shank to fit on a 1/2-inch router Works with all 1/4-inch shank router bits. Hardened alloy steel with polished finish. Slots in the body allow collet to tightly grip 1/4-inch round shank. Length: 1-inch, External Diameter: 1/2-inch, Internal Diameter: 1/4-inch