Name: GapChek (TM) from Warburton
Brand: Warburton
SKU: GPCK
Price: 120 USD
Availability: InStock
Rating: 4 (1 reviews)

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GAP CHEK


Invented by Ken Titmus at Warburton USA, 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 sizing of the mouthpiece receiver and the position where the lead pipe is soldered into the receiver exactly the same - and trumpet mouthpiece receivers would never wear - and mouthpiece shanks would all be exactly the same size taper. In reality, these perfect conditions don't exist - which in turn results in variations in the amount of GAP. To complicate things a little more, there is no single "correct" GAP size. The amount of GAP can and will vary between great playing mouthpiece/trumpet combinations. Too little or too much GAP causes playability problems which can be very difficult to overcome.
GAP too large: Lower register becomes stuffy Upper register may reach a "wall", above which resistance can not be overcome GAP too small: Lower register very free-blowing Poor definition to the notes above high C Lack of healthy resistance causes upper register to "airball", or wash out There is nothing to "lean on" when coming back down from a high passage	If you own multiple horns and/or mouthpieces, you should also own a GAP CHEK
What SHOULD the GAP be? GAP CHEK has reference lines inscribed every 0.050 inches (fifty-thousandths of an inch). Our experience shows that the "sweet spot" for the GAP is usually somewhere between 0.100 and 0.150 inches (between 2 and 3 lines). Of course there ARE exceptions to this. If your horn/mouthpiece plays well AND the GAP is within the typical "sweet spot" range of 0.100 to 0.150, then you probably will NOT gain anything by altering the GAP. If you are having any of the playability problems described above, then you MAY be able to improve or eliminate the issues by altering the GAP, especially if the GAP is outside the typical "sweet spot" range. If your measured GAP is more than 4 or less than 2 reference lines AND you think your horn plays OK, you still MAY find some improvement by altering the GAP to be within the typical "sweet spot" range. There are several ways to correct GAP problems: Use a different size mouthpiece shank. We offer oversized and undersized mouthpiece backbores with a threading system to help with this. If you use a one-piece mouthpiece, try a different one - or switch to the top/backbore combo we offer here at ACB. Replace your worn trumpet mouthpiece receiver. Usually not a desirable option because the soldering process requires refinishing the trumpet - plus the risk of introducing new problems by altering the trumpet itself. If you have additional questions send us an email. Prior to ordering please check our Shipping and Returns policy. Also note weight indicated in the ad is shipping weight not actual weight of the item.

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1 Review

4
Warburton Gap Check tool.

Posted by Stu Matlow on 29th Jul 2026

Although it’s possible to measure trumpet mouthpiece gap using a bamboo skewer, Sharpie and ruler, this Warburton tool is far easier, faster and more precise. After doing my own horn, I lent the Gap Check to section-mates. The gap in my 60-year-old SilverSonic was a half inch. I cut the end off of an unused mouthpiece and machined it to fit the receiver for a .1 gap. This really opened up the upper register. This is a useful tool to make a useful measurement.

GapChek (TM) from Warburton