I have purchased and installed the castor set (K&M Wheel Set for Guardian) that go with the K&M 17515 model to make cleaning around the rack much safer and easier. The guitar rack rolls very smoothly (on a hardwood floor and stage, I haven’t tried it on carpet…) even when full of guitars and there is no fear of any guitars falling out. Each wheel has an independent locking system to assure the rack will not move unexpectedly.
I would, with all certainty, recommend this to anyone with a need for it.