Wrong forum, but yes, they're aluminum.
They hold up pretty well.all things considered. I've warped a baseplate on one, but put it in a vice and bent it back and am still riding on it. Ride ratchets suck. They stick bad and always have.
If you're looking into the SPi's make sure you want a stiff binding because they are STIFF.
"People say that marijuana smoking is going to get in the way of my career. I say to them that on the contrary, my fighting career is getting in the way of my marijuana smoking." -Nick Diaz