The overall length with mouthpiece removed is 12 1/8" and bell diameter is 4 7/16". The bore measures .464".ECHO CORNET is unique have fourth piston valve, and a second bell, which tapered in the opposite direction as compared to the main bell. The airflow is redirected to the second bell (by depressing the fourth valve) a muted effect Has been achieved, not unlike that resulting from the use of a metal Harmon-style mute. Typically the echo bells are "attachments" which are removable, so the horn can be held and played conventionally. But the fourth valve is a permanent part of the valve cluster itself.