Griego Oft / Ωft (Oft Series) Model Number: Oft 3.5 / Ωft3.5  Compatibility: For Tenor Trombone (Large Shank)  Cup Diameter: Approx. 26.16 mm Throat Diameter: Approx. 7.11 mm Finish: Silver-plated  This is said to be the largest model (3.5) in the Toby Oft series. It is considered quite rare to find this model on the used market. - The low register is thick and rich, and the high register is also very easy to play. The overall impression is good balance across all registers. This mouthpiece was very helpful in developing my low register on the tenor bass trombone.