Replacement wheel frame arm.  Specify right or left side when viewing from the back of the cart facing forward.  Will fit older versions of the cart but the stowage hole about 6" behind the angle bracket may need to be redrilled to match.  Simply line it up with your old arm and drill.
 
Note:  Right side is out of stock and we anticipate restocking in April.  If you need a right side send us an email to get on the list.