Porter-Cable® 42048 template guides are a great way to guide a router for a very controlled cut using a pattern or template. The guide attaches to the router base to keep the bit a specific distance from the template's edge while allowing the bit to cut in where needed. Porter-Cable® Template Guide, 1-35/64 in OD, For Use With: Standard Router, Specifications: 1-3/8 in ID, 17/32 in Distance Past Base, Steel