Bore sizes for the slide of the contrabass trombone are typically in the 0.567 to 0.635 inches (14.4 to 16.1 mm) range; the most common sizes on contrabass trombones in F are between 0.567 and 0.580 inches (14.4 and 14.7 mm) as the larger sizes are usually reserved for the contrabass trombone in low B ♭. The bell diameter is typically 10 to 11 inches (25 to 28 cm).
About Tenor Trombones: A descendant from the 18th century (Baroque period) instrument known as the sackbut, the modern trombone has remained relatively unchanged in the past 100 years. The most popular trombone is often referred to as the tenor trombone, due to the approximation to the tenor range of the human voice.
A Soprano trombone has a more trombone like smaller bore of around .420-.430" and the better ones use a smaller shank mouthpiece like a modern cornet. That mouthpiece should have a deeper cup and larger throat than a trumpet mouthpiece. It will have either no tapered lead-pipe or a short one with little taper as it is with trombones.
The tone of the alto is more brilliant than that of the tenor or bass trombone. The bore of an alto trombone is similar to that of a small tenor trombone - usually around 0.450 to 0.500 inches (11.4 to 12.7 mm) with a 6 1 ⁄ 2 or 7 inches (17 or 18 cm) bell.
Trombone bell size is equally as important as the bore size when comparing the various types of trombones. Different sizes and thickness can impact sound, and more advanced musicians may have preferences for bells with certain features. Bass trombones usually have larger bells than tenor trombones.
A tenor trombone is always tuned in Bb, but unlike the trumpet, it is a non transposing instrument. There are two main types of tenor trombones worth knowing of, the small bore trombone and the large bore trombone. Each of the two can be fitted with an F attachment.
It is also seen in military bands, brass bands, jazz bands, wind ensembles, and a variety of brass groups; the bass trombone is usually played by the third trombonist in a symphony orchestra trombone section, the first two parts usually being played by tenor trombones.