I got to use these while driving school buses in the Rocky mts. Awesome! The Thomas buses I drove had an automatic Telma brake and the Blue Birds had 4 stage manual brakes. The 4 stage was awesome, like having a hand brake! Awesome in snowy parking lots. lol They slow you down A LOT. They all had an overheat light that no matter how hard I used them I never saw it come on. The skoolie I own doesn't have one and I smoke the brakes out here way more than I'd like to. I'm sure they're expensive to get from Telma and I doubt anyone that has one would have any reason to get rid of them.