Yamaha Bass Trombone Model No. Inner Rim Diameter (mm) Rim Contour/ Thickness Cup Depth Throat (mm) Backbore Playing Characteristics 58 26.84 standard/ standard standard 7.25 semi-wide Medium cup and rim for easily playability through the low and middle registers. Crisp attack with outstanding flexibility. 59 27.22 standard/ semi-thin standard 7.25 semi-wide Relatively thin rim. Rich sound even on pedal tones. Voluminous cup for solid lows and plenty of power. 60B 27.83 standard/ semi-thick semi- shallow 6.92 semi-wide A German-style combination of fairly thick rim with relatively shallow cup. Excellent flexibility. Easy playability and clear tone in the middle and low registers. 60 28.25 standard/ thin standard 8.10 wide Very deep cup with a large throat and backbore. Powerful, deep, low tone. For advanced players.