Specifications Key: TU331BB: Bbb Dual bore: 16.89/17.45 mm (.665/.687") Bell: Upright, 457 mm (18") Action: Front-action Pistons: 4, Monel Waterkeys: 4 Slide material: Brass Mouthpiece: HTU335-18 This model Holton tuba had been replaced by the 440R. We are able to offer this discontinued model at incrediable savings. Call Mark or Simon for more info.