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Rim Size Reality – A common sense approach


Mouthpiece rims are not only a size, but a shape. Because of this relating measurements to how the rim will feel to you, as a player, is extremely difficult, if not impossible. Unlike a washer for a bolt, in order to measure the diameter of a mouthpiece rim, you must choose a point along the curve to designate as the “measured diameter.”

Different manufacturers measure at different places and this adds to the difficulty and confusion. Additionally, although a diametric measurement can be a guideline it is not an absolute as to how big or small a rim will feel to a player.

The diagram to the right shows two different rim shapes that both measure the same diametrically at the “flex point (the point where the curvature changes from convex to concave which is a logical point to measure from a manufacturing standpoint). It is easy to see however, that these two rims which “measure the same” would “feel” very different to a player.

You may note, for example, that many Bach rims measure the same at a given point, but “feel” very different in diameter when placed on your lips. This, obviously, is because they have different shapes which, like the drawing above illustrates, will affect how they feel to you, the player.

In Bach sizes most players report the rims feel larger to smaller from #1 (largest) through #20 (smallest).

Additionally, your individual tooth structure, how fleshy your lips are, and even the “breathability of the mouthpiece can affect how a rim feels to you.

“Breathability” means how much “back pressure” the mouthpiece gives you. If the mouthpiece has a lot of back pressure, it will keep your lips from penetrating as far into the cup as they would if the mouthpiece has less back pressure. This will affect how your and where lips contact the rim, thus affecting the “feel” as well.

We recommend taking a very simple, yet logical, approach to rims. Hold a rim to your lips and see how it feels. If it feels too big or too small, accept that it is regardless of what any measurements say.
If it feels just right, accept that as well.