This is a base plate that fits a Porter Cable router.  I needed a larger base plate for a jig so I designed this one with a 7.125 diameter base.  (This entry also includes a standard 5.75 inch version in case that's useful.)  I used a CNC to mill mine from polycarbonate but perhaps you're interested in 3D printing yours.  Also included here is the Fusion 360 design files in case you want to start with this and modify it yourself.