This conversion kit is engineered to replace bushings with smooth high quality precision bearings. One kit will convert both wheels and includes all required hardware. Maintenance is optional: All bearings are sealed with grease so they are maintenance-free, however the outer seals can be removed if you prefer scheduled maintenance. Thank you for all of the support and positive feedback! The support has allowed us to continue offering solutions and improved products at distributor direct prices. New products coming soon !!.