Energy Suspension 2-1/4in Tall x 3-9/16in Dia Black Coil Spring Damper Donuts (Set of 2)

Made of superior formulation Hyper-Flex(TM) polyurethane and uses high precision bearings. Experience little or no rolling resistance! The unique polyurethane material and design allows smooth, unimpeded rolling for indoor/outdoor ease of movement over cracks, washers, misc. debris, etc.