You can usually locate the manufacture's product label on the mast section of your Hoyer Lift. The label should have a model and serial number. You can also identify this lift because it has a painted frame instead of chrome.
Refer to drawing for available replacement parts for the Hoyer HML400 Lift.
#222-6007 is set of 4 caster wheels, 1 locking, 3 non-locking.