In general each of our footrests are delivered with a set of 4 support rings (plus one replacement ring).
This replacement set of 2 pieces can be ordered extra in case you lose the rings or need some spare.
Please keep in mind that the swop of humidity and cold A/C conditions (in case you might use the highchair outside) might have an affect of the Support Rings which are made out of rubber material which widens in hotter conditions.
Also, the usage of strong cleaning products might have an affect of the life span and function of the rings. Best to clean your highchair with a soft dish washing liquid and to make sure that the surface of the legs is dry again and free of soap before installing the footrest.