Designed to securely hold router bits, the Porter-Cable 42950 1/2-Inch Router Collet is compatible with Porter Cable router models 690, 9690, 691, 693, 693PK, 7529, 97529, 7518, 7519, 7538, and 7539. Featuring an auto-release design that prevents router bits from sticking in the router, the 42950 can be used two ways: as a straightforward replacement collet, or to enable a router to handle shank bits measuring 1/2 inch. Its clever design also allows the router bit, collet, and collet nut to be removed as a single, unified unit, which helps prevent any time-wasting, immoveable bits that won't budge.