controllable pitch tunnel thruster Fixed Pitch Tunnel Thruster Diameter 500-2100mm. Eletric or engine drive. CCS ,BV ,ABS, N Fixed Pitch Tunnel ThrusterStern Thruster:1.Diameter 1000-2800mm.3.Eletric or engine drive.4.CCS ,BV ,ABS,NK, etc.Tunnel thruster hydraulic system selection,power selection , blades size selection , the transmission way choice-Superior Strength Tough and rational structural ...