Amado Water Key:
This is common feature that many manufactures offer on their instruments. Instead of the traditional lever, cork and nipple, there is a machined barrel soldered on with a small stainless steel piston inside it. The piston inside allows the inside surface of the tube to remain smooth and virtually seamless when in the closed position instead of a large drop-off where the nipple would extend out to the cork. Obviously if a node where to hit on this spot of the horn the pitch and/or sound of the note would be seriously affected. This is common for C and 2nd line G on most C trumpets in the main tuning slide water key. You may have seen some people play with their main slide upside down on C trumpet in an effort to "quick-fix" this dilemma. Having the Amado Water Key installed, would alleviate this problem.