"Get ready to rip with the Phelps Game Calls Unleashed Bugle Tube Elk Call! Large corrugations in the chamber deliver great resonance and provide structure to the tube. Thick walls ensure extreme volume with no plastic sound. An over-cupped exhaust bell creates backpressure and resistance, making it easier to use all diaphragms. 1.25"" flared mouth opening is comfortable to use. Large corrugations in the chamber for great resonance Thick walls for extreme volume with no plastic sound Over-cupped exhaust bell creates backpressure and resistance Comfortable 1.25"" flared mouth opening"