M17.75N Specs: ID of 17.75mm / .699 inches OD 25.75mm / 1.015 inches Rim Width 4mm / .177 inches ID at rim/ cup joint 17.5 / .689 inches Details about Wedge Horn Screw Rims: Wedge French horn mouthpiece rims are available with 750-36 threads (compatible with Moosewood, Giardinelli, Osmun, and Houser mouthpieces), and with _ÇÎÎÇÎ¢ÎÎÎ£Î_ÇÎ±metric_ÇÎÎÇÎ¢ÎÎÎ£ÎÎÇÎ 800-36 threads (compatible with PHC, Paxman, and similar European mouthpieces). Rims are available in four inner diameters (ID), ranging for 17mm (.669 inches) to 18mm (.709 inches). The ID of Wedge mouthpieces is measured at a depth of .04 inches into the cup, measured from the crest of the rim. Rim widths range from 3.75 mm (XN) to 5 mm (W). 800-36 _ÇÎÎÇÎ¢ÎÎÎ£Î_ÇÎ±Metric_ÇÎÎÇÎ¢ÎÎÎ£ÎÎÇÎ Rims Metric rims have the same OD and ID as the 750-36 thread rims, but the rim height is .130 inches to correspond with the design of PHC rims. The joint diameter on these rims varies slightly as the ID gets smaller, from 17.5mm (.689 inches) on the 18mm, 17.75mm, and 17.5mm rims to match PHC cups, down to .666 inches for the smallest 17mm ID rims. The smaller rims have a slight overhang, similar to PHC US1 and US2 rims. This allows players to use a rim with a smaller ID on the larger PHC cups.