I've tried those, but found they roll *too* good for my taste...I don't want my games moving under hard play...then again my games are on smooth concrete as opposed to carpet. I prefer having 2 fixed and 2 swivel w/brake as opposed to 4 swivels, as having 2 fixed casters allows easy steering. All 4 casters as swivels makes the game hard to move in the direction you want, kind of like the shopping carts at most Trader Joes. I use the kind you get at home depot and install them using self tapping #10 x 3/4" wood screws, no drilling required. Not sure if they mar or not, but haven't noticed anything like that so far...Too bad Home depot doesn't sell theirs with that kind of wheel material. However casters of any kind are superior to sliders or levelers.. it's nice to see others that feel the same way

makes moving games for maintenance or gameroom re-arrangement such a breeze. Every game in my collection has received the caster treatment. The only downside is the surface they ride on must be truly level otherwise the cab might wobble. But this is easily solved by putting shims or cardboard under the wheel that isn't touching the ground.
Tom