I like the B-Square 3/8" groove to Weaver-style ring adapters. They are a 2-piece set of adapters that allow you to use whatever brand of Weave-style rings that you like. I have them on several rimfire rifles that didn't come factory d&t, like the current Marlin and Savage bolt guns do, and also on a couple of Savage 24 combination guns in both .410 and 20 gauge.
They run around $25 to $30 per set, but are well made and, IMO, well worth the price.
