HI Tom
See the item below, the pin holes are under the router base, quick and easy to setup just put the pin in the stock set the jig on the hole size you want plunge the router down and cut the circle out, no need to adjust it because the scale is in 1/16" ,you can use a 1/4" bits or 3/8" or 1/2" what every the hole size needs to be by using a bit size bigger that will move it by a 1/32" the norm.
Note **** I did find one error with the Jasper jig, the mounting holes are drilled to deep in the jig, you only have a 1/16" of plastic to mount the jig to the base plate of the router but that's not big deal when you use the 3/4" brass guide because you don't need to bolt it to the jig anyway, see snapshots below ,just drop it in the hole and make the pass, but you can bolt the jig to the base plate if you want.
See reviews on Amazon, some have snap the holes out when they use the jig but that's why a made a copy of the jig in 1/2" MDF when I have the need to bolt it to the base of the router,like when I need to put a hole in the side of a project or the underside of one..just more control of the jig and the router.
Some will say if you drill the jig out to 3/4" you just lost the way to line the jig up to the base of your router well not true just take some 3/4" dowel rod and put in a 1/4" hole in the center of the wooden dowel to hold the 1/4" steel dowel pin that comes with the jig, slip in the wooden dowel rod with the 1/4" dowell pin and chuck it up in the router and bolt the jig to your router.
The 3/4" plug is easy to make, BUT it must be true (dead center) chuck it up in the lathe let the lathe spin and use the center to mark the end for dead center, if you have a drill chuck for your lathe drill it out if not just mark it with the dead center tool and then use the drill press to drill it out true.
Then press in the 1/4" dowell pin and your done.
I made mind with some Alum. round stock that looks like a 1 1/2" over size washer that has 3/4" O.D. dog ,that's is 1/4" long and a 1/4" hole in the center for the dowell pin, but I used a metal lathe to do that with.
Bj