First of all the Polaris robotic cleaner could have been a great product if the manufacturer had built in longevity instead of planned obsolescence. The plastic parts have a short life span and are expensive to replace. The wheels are made of thin abs plastic and the hubs have no structural integrity. Since all of the parts are unique only to this brand and type of cleaner, the manufacturer can charge whatever they wish and often at inflated prices. The fact that you cannot purchase a wheel with out buying a tire is pure extortion. Some improvements have been made to the rear wheels by adding more reinforced strength at the hub. But I surmise that any improvements to parts are only after inferior parts inventory has been sold off or enough complaints have been received. It appears the plastic bushings and gears were also made to be consumable items rather than a integral part. Sunplay has the best prices for replacement parts for this cleaner, but still high and not a good value. Pool cleaners always follow a common scenario: priced high to buy then gouge them on parts.