Edwards Bb/F Axial Flow Tenor ValveThe Edwards Axial Flow Valve is the most open trombone valve on the market. It gives the player the ability to blow freely in all registers as it maintains the same sound and feel on the Bb and F sides. Combine this with the valves open wrap design and the T350 E and T350 HB behave much like a straight tenor while giving up none of the versatility of a valved instrument. Your Edwards Axial Flow Valve will provide you with a lifetime of use if properly