Its a brake. There's not much to it.
I bought this brake to go on my Jester bindings mounted on my new Pontoons. There is no reason for these to be this expensive and Marker should sell the size brake you need for your ski and not make it an extra. Especially when the jester is the recommended binding for the Pontoon. I doubt the brake will even do anything if I'm skiing in the powder that I hope to be with this ski and it comes off.