Two versions
Williams makes a much smaller one in their WGRS line. It is the WGRS -54. The Brownell catalog says it can be fitted to most dovetailed receiver 22's. It has sliding adjustments, locked with a screw. I've sometimes had to file it slightly to fit the grooves. Retail price in my 1 1/2 year old catalog is $30.25
The one the other post mentioned has more adjustment, kind of a micrometer adjustment, but it is BIG, larger than the common Foolproof sights. Model is FP-GR with screwdriver adjustment, FG-GR-TK with target knobs. List price is $59.95
Bruce Pryor