Keep Your Motors running at Peak Performance by running them "Nice & Cool"! These water jackets allow the circulating water to come in direct contact with the motor casing. This is a much better alternative to a basic cooling coil! Water Jacket for 600 brushed & Feigao 540 brushless Sized Motors.Measures 30mm wide.Fits 35-45mm Diameter Motors.For motors that have cooling vents, a piece of shrink wrap is provided to cover the motor casing then install the Jacket over it. They come with a combination "hull bottom water pickup/exit fitting" and approximately 15" of tubing.