Profile: Poly-Flex, Inc. specializes in blow molding technology. We produce cart wheels, plastic wheels and blow molded cases. We stock a full line of wheels in various sizes including 4, 6, 8, 10 and 12 inches. These wheels are available in black walls or white walls. Our Snap-On™ self-locking wheel system provides strength to the wheel design and eliminates the need for pail nuts or any other form of wheel retention devices.