I've seen that in the Duluth catalog and in some tool catalogs. Seems like a good idea, but I've always just run a 2x4 over the table saw and made my own. I'd use oak if going all the way to 3/16".
I don't begrudge them $7 for a handy jig, but I've never wanted to wait a few days and pay $10 for shipping so I DIY.
For those radiused sections: use a hole saw in your wood block, say a 1" diameter. Then, using the same pilot hole, use 1-1/8", 1-1/4", etc. Trim the random thin bits away with a sharp chisel and you'll have a perfectly circular core as a part of your jig.
They have 4 positions for 2 studs of fixed diameter. Bolts are CHEAP. Holes are free. Give yourself lots of options by dropping various diameter bolts into numerous holes in your jig. Heck, don't stop at bolts - step up to 1/2", 3/4" and 1" wooden dowels.
Try a set up with coat hanger wire first. When you've got it dialed in, use the good stuff - stainless or Ti. Or just paint the coat hanger wire!