It fits ALL Porter-Cable routers,  models no.: 690, 690LR, 9690LR, 690, 691, 692,693, 890, 891, 892, 893,  7518, 7519, 7529, 7536,7537, 7538, and 7539. Includes one collet and locking nut assembly

Use 1/4-inch shank router bits with your 3-1/4-hp Porter-Cable router or just replace a lost collet with this 1/4-inch auto-release collet.  This collet is required in order to use smaller, 1/4-inch shank bits with these routers. The auto-release design prevents bits from becoming "frozen" or stuck, since the collet and collet nut come out as one unit. The collet, and collet locking nut, are one unit, which will help prevent loss.This 1/4" self-releasing collet allows the woodworker who already purchased 1/4" bits to use the older bits , saving the cost of purcashing new 1/2" bits.   If you've ever delt with a frozen router bit, you'll appreciate the self-releasing feature.