Ball bearings are what make things spin and in X-Jets hose swivels and thrust nozzles, the life of the friction free hydroflight party. Hard round balls that ride in precision machined channels, taking up all the stresses and force and letting you steer and fly with precision. The balls have to resist salt water corrosion, metals are out of the question, so the first choice is Acetal, POM Copolymer (Delrin®) (Celcon®) (Acetron®) engineering plastic with great wear resistance. What if you want to spring for the next level of friction resistance to alleviate the occasional sticking of the action of your board or jetpack when you have grit in?
Ceramic ball bearings are a step up in performance, they are hard, harder than almost any other materials. They are twice as hard as stainless steel and an in an entirely different class of hardness than conventional Acetal bearings, incomparable. Hard means they roll easier, grind up sand granules and never need lubrication, completely resistant to absorbing water and will never corrode, will never wear out.
Ceramic bearings are performance items and are expensive, for the rider looking for every advantage, they are unbeatable. Ceramic, M8 (actual 7.93mm), G5, 128 pieces in a set, for the Jetblade by X-Jets. $620, free shipping.