Be aware that they are a lot heavier than pneumatic ones and not forgiving at all when going over bumps. My PF trolley came with them, but I took them off and replaced them with pneumatic ones for these reasons. The pavements where I work are quite rough in places. I find the trolley feels a lot nicer to use as well if you keep them at about 20psi. I keep spares in the vehicle just in case. You can change them in seconds.