Description: The new 5 blade special skew propellers are the result of over 2 years of development work and thousands of tests. They have been designed to reduce the noise level, while maintaining the exceptional efficiency of the old 4 blade Side-Power propellers. This goal was achieved, and we even chose to make them a little bit more aggressive on some models, increasing the thrust on some thrusters about 5%. Please see individual information on each new thruster for more details. Details: · Noise reductions of up to 75% measured in controlled environments · The expected and tested normal noise reduction in average installations: 20-40% · Will be delivered on all Side-Power models except models with 300mm and 385mm tunnel diameter · Upgrade kits will become available for most SP series thrusters with special adaptors