Foam or drift tires for that particular lot maybe. Never heard of ARRMA, so I'd imagine parts are hard to come by locally for me. Actually, that's probably true for everything except Traxxas and Losi. (Although HobbyTown will order to store without shipping)

It's been a while, but I used to build brushless motors on a line. I remember the design advantages. They seems to be coming way down in price, which is encouraging.