Osmun metric rims measure 17.5mm where they meet the cup and have Paxman Halstead-Chidell .800″-36 threads. They fit Osmun metric cups as well as those from Halstead-Chidell. Osmun rims are available in five inner diameters in .5mm increments from 17-19mm. Osmun standard finish is gold over silver plate. Gold is hypo-allergenic, non-tarnishing, and feels soft and slippery on the embouchure. Delrin and Lucite rims are temperature neutral and work well for players who use a dry embouchure. Osmun plated finishes are very durable and, with normal care, can be expected to last for several years of heavy use.