This is one Pentair R201557 Ball Bearing Wheel for the ProVac Flexible Vac Heads. This replacement Rainbow vacuum head wheel #175 is made of long wearing polyurethane with Delrin inner race and stainless steel balls.
This replacement wheel part is designed for the ProVac Flexible Vacuum Head and these Pentair ProVac models: #214, #222, #229, and #241 (including Residential Models).
