I recently acquired (from a TromboneChat member – thanks Jon!) a used AR Resonance mouthpiece with a water buffalo horn (!) cup and rim. This particular one (small-shank) is labeled 25.10 V+ 60. That means that the Rim I.D. is 25.1 mm; the Cup is rather V-shaped, and the Throat is 6.0 mm diameter. In other words, about the size of a Bach 6¾C, a Schilke 47C4, a Yamaha Nils Landgren, or perhaps a Conn 3 – but different from all of them.
The buffalo horn feels good on my lips, and the rather flattened rim is very comfortable; it’s an easy blow. After playing it for a few hours (on a small 0.500" bore trombone), I find that I really like this mouthpiece. The sound is pleasant – warm, light and lively, a little less edgy than a brass mouthpiece. I’m afraid to fall in love because of the price (~$235)!

These mouthpieces are apparently available in the U.S.A. from another TromboneChat member, Luke Malewicz:
https://www.chicagojazztrombone.com/arr ... outhpieces
Anyone else have experience with these mouthpieces?