The Harmony Axle Clips are replacement round clips for the Harmony Stowaway, Boat, and Sit-on-Top carts. They are compatible with the beach wheels, all-terrain wheels, and the flat-free wheels. Each cart has 2 round clips that slide in to the hole closest to the end of each side of the axle.
A little expensive, but much better than the cheap clips that came with my cart. Worth the money.