The Model A Mounting Bar was initially designed to fit our edge-guide onto the Porter Cable 100, 690/693 and 890/893 routers. We have also made it the standard mounting bar to be used with our  Clamp Interfaces, Ellipse Jigs, and Sub-Base Assemblies (so if you are purchasing any of these items, you will also need this bar if you don't already have it. Not sure if you have it? Call us at 1-800-480-6427 and we can check your customer card).