All aluminum mute can be used as a straight mute, cup mute or plunger mute by attaching or detaching the special removable cup section. When completely assembled it is a cup. Remove the cup and it is a straight. Or, use the cup portion by itself as a rigid plunger. Intended for use with smaller trombones, pro, intermediate and student, with bell sizes of 8 inches or smaller. Will not fit contemporary wide-throat models such as the Yamaha YSL-354. Made in USA. -cdp