Bach Trombone Mouthpiece Guide
The single most important decision in trombone mouthpiece selection: small shank or large shank. Everything else is secondary. Here's how to get it right.
Small Shank vs. Large Shank
Trombone mouthpieces come in two shank sizes. Using the wrong shank changes the gap between mouthpiece and leadpipe, which can noticeably affect intonation, slot feel, and tone color.
How to identify your shank: If your instrument is a Bach 36, Yamaha YSL-354, or any standard student tenor — use small shank. If your instrument is a Bach 42B, 50B, or any dedicated bass trombone — use large shank. When in doubt, measure the receiver bore — it will be approximately 25.4 mm (1.000″) for small or 28.6 mm (1.125″) for large.
Small Shank (Tenor)
25.40 mm (1.000″)
~42 mm
Bb tenor trombones: Bach 36, 42 (in small-shank config), Conn 88H (optional), Yamaha YSL-354, King 607, most student-line instruments
The most common trombone shank. All of Bach's numbered suffix-only models (e.g. 6.5AL, 7C) without a bass designation are small shank.
Large Shank (Tenor / Bass)
28.58 mm (1.125″)
~45 mm
Bach 42B, Bach 50B/50B3, Conn 88H, King 5B/7B, Shires TBQ42, Yamaha YBL-421 bass, Edwards bass trombones
Large shank is required for all bass trombone instruments and is offered as an option on some .547 bore tenors (Bach 42B-series). Models with "B" designation in the suffix are large shank (e.g. 5GB, 1.5GB, 4GB).
The G-Series Explained
Bach uses a different cup designation system for trombone than for trumpet. The "G" suffix describes a wide, smoothly contoured cup bowl distinct from the orchestral cup shapes used in trumpet mouthpieces.
The trombone default. Wide, smooth rim with a generous cup bowl. Produces warm, full orchestral tone. Slightly deeper feel than the AL series. Most orchestral players use a G or modified G cup.
Slightly shallower than G, with a more defined cup-to-throat transition. Produces a brighter, more focused tone preferred for commercial, jazz, studio, and commercial orchestral work. The 6.5AL is the world's best-selling trombone mouthpiece.
Carry over the trumpet suffix logic. Shallower than G. Rarely used for standard trombone — more common in alto trombone and commercial applications where a very bright, compact tone is needed.
Bach Trombone Model Table
| Model | Rim (mm) | Shank | Cup | Primary Use |
|---|---|---|---|---|
| 1.5G | 27.00 | Small | Deep G | Large orchestral; maximum volume and projection |
| 2G | 26.72 | Small | Deep G | Orchestral bass range; rich fundamental |
| 4G | 25.40 | Small | Deep G | Orchestral all-around; full and centered |
| 5G | 25.40 | Small | Medium G | Section playing and orchestral; balanced tone |
| 5GS | 25.40 | Small | Medium G | Same as 5G with wider, smoother rim contour |
| 6.5AL | 25.40 | Small | Shallow AL | The most popular Bach trombone mouthpiece; commercial/jazz/all-around |
| 7C | 25.40 | Small | Medium C | Student default; less open than AL suffix |
| 12C | 23.00 | Small | Medium C | Smaller rim; alto trombone or small bore tenor |
| 5GB | 25.40 | Large | Medium G | Bass trombone; orchestral section and principal |
| 1.5GB | 27.00 | Large | Deep G | Bass trombone; maximum volume and bass register |
| 4GB | 25.40 | Large | Deep G | Bass trombone orchestral; balanced depth and response |
| 2GB | 26.72 | Large | Deep G | Bass trombone; rich, dark orchestral voice |
Source: Vincent Bach / Conn-Selmer official catalog. Rim measurements are approximate inner playing surface diameters.