Harrelson Shim Kit to reduce gap: A Survey of Thirty-one Mouthpieces

We have already taken several orders for the new Mouthpiece Gap Shim Kit, which includes 10 precision machined brass tubes designed to reduce gap. You could dramatically improve the playability of your current setup by doing the following:

1) Measure your current gap
2) Determine your target gap - usually .060 to .100 inches
3) Wide Gap: Insert appropriate gap shim inside the Mouthpiece Receiver of your trumpet
4) Narrow Gap: Reduce length of mouthpiece shank
Note: Installation is easier with the new Venturi Measurement Tool (VMT) and measuring gap with the new Gap Measurement Tool (GMT). You may also purchase the entire Gap Solution Set.

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Example 1 - Monette B4S

Goal: Increase flexibility, lessen resistance

Original Gap: .138"

Gap Shim Size: .040"

New Gap: .098"

Expected Result: More open air flow, balanced flexibility & slotting

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Example 2 - GR 64S

Goal: Decrease hard slotting, increase flexibility, lessen resistance

Original Gap: .167"

Gap Shim Size: .080"

New Gap: .087"

Expected Result: Hard slotting in upper register is replaced with even scale and arpeggio, flexibility when playing wide intervals is greatly improved, air flow is increased

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Example 3 - Bach 1C

Goal: Achieve a gap of zero allowing the maximum flexibility & air flow

Original Gap: .020"

Gap Shim Size: .020"

New Gap: .000"

Expected Result: Zero gap is sometimes preferred by players accustomed to open air flow and extreme flexibility. This setting requires a very good ear as intonation on each note is determined more by the player.

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Examples of Mouthpiece Gap variations by Manufacturer and Model
The following gallery shows 31 different mouthpieces inserted into a Harrelson trumpet receiver. This illustrates the corresponding gap variations present among various mouthpiece taper lengths.

The Harrelson Receiver taper and length was designed to minimize gap when used with most standard mouthpieces. When ordering a Harrelson Trumpet while using a Monette mouthpiece, the gap is almost always reduced by means of moving the leadpipe closer to the receiver taper to compensate for the extremely short shank length. The opposite is true if a client states they primarily use Schilke or various Bach mouthpieces. Bach mouthpieces typically vary in length by as much as .12 inches and are a major source of gap issues. Yamaha mouthpieces are not shown, but consistently measure slightly shorter than vintage Bach mouthpieces.

Bach (Gap: .005 - .02) Bach mouthpieces typically vary in length by as much as .12 inches and are a major source of gap issues.
Schilke (Gap: 0 - .08) Schilke mouthpieces commonly have a long shank creating very small gap.
Click on photo for gap measurements, make, model information

GR (Gap = .056 - .167) GR mouthpieces have the widest gap variance of any modern manufacturer I have measured.
Marcinkiewicz (Gap = .08 - .11) Marcinkiewicz mouthpieces are consistently within range of acceptable gap on most trumpets.
Reeves/Stomvi (Gap = varies) the Stomvi/Reeves Flex Sleeve 4.5 produces a .100" gap. Interchangeable shanks ensure a perfect fit.
Click on photo for gap measurements, make, model information

Harrelson (Gap = custom designed to your playing preferences and determined before the trumpet and/or mouthpiece are made)
Click on photo for gap measurements, make, model information

Monette (Gap = .112 - .143) Monette mouthpieces consistently have shorter shanks and larger gap translating to hard slotting.
Click on photo for gap measurements, make, model information

Warburton (Gap = .085 - .107) Warburton mouthpieces often produce gap close to the average target of .100".
Austin ACB (Gap = .076) Produced by Pickett, the ACB produces less gap increasing flexibility and airflow.
Stork (Gap = .109) Stork mouthpieces often produce gap close to the average target of .100".
Taylor (Gap = zero) Taylor mouthpieces do not always fit other brand receivers.
Callet (Gap = .075) Produced by Kanstul, this Superchops I offers the more desirable slightly smaller gap.
Curry (Gap = .048) Curry mouthpiece shank lengths vary by model, I suspect to achieve results related to their purpose.
Wick (Gap = .123) I have measured relatively few Wick mouthpieces. In this case, closing the gap with a .020 shim is advised.
Greg Black (Gap = .115) I have measured relatively few Black mouthpieces. In this case, closing the gap with a .020 shim is advised.
Click on photo for gap measurements, make, model information

Remember, the steps to measure and adjust gap:
1) Measure your current gap
2) Determine your target gap - usually .060 to .100 inches
3) Wide Gap: Insert appropriate gap shim inside the Mouthpiece Receiver of your trumpet
4) Narrow Gap: Reduce length of mouthpiece shank
Note: Installation is easier with the new Venturi Measurement Tool (VMT) and measuring gap with the new Gap Measurement Tool (GMT). You may also purchase the entire Gap Solution Set.