GAP CHEKScroll down for instructions! Invented by Ken Titmus, this handy little tool measures the distance between the end of your mouthpiece shank and the beginning of the lead pipe in your trumpet receiver known as the "GAP". Did you ever wonder why a given mouthpiece works well in one trumpet, but not very well in another? Often times this problem can be traced to the GAP being too large or small. In a perfect world, all trumpet manufacturers would get the