When we started designing the Wataboard we tested many different hose sizes. We tested hoses from 101mm all the way to 152mm. Eventually we settled on 115mm because it was the perfect balance between rider experience, jet thrust, and jet ski fuel efficiency. A 115mm diameter hose allows for greater volume of water flow than a 110mm hose. This translates to much greater thrust at lower engine RPM. So you fly higher and save fuel at the same time.