Rogers did three sorts of collet plates for different tom and leg uses - depending on number of toms and size of bass drum, for example, they did 90, 75 and 60 degree plates (these also doubled for bass drum leg holders, etc.
There's a thread I started about this on the main forum and someone did a nice diagram but essentially the angle makes up for the curve of the drum, ensuring the Swivo post goes straight up (if that's what you want). It all seems to have been a bit after one's own wishes.
For my two bass drums (18" and 20") I've figured I need 60 and 75 degree plates respectively. The challenge is most people don't carry a set square around so they kinda guessing if it's a 60 or 75 (though one of our guys in here from Belgium just so sold me a 60....and he did have a set square to check the angle...and he photographed it - this is why Europeans kick butt).
So if you've got one that's a bit less than a right angle, it's probably a 75. I'm still after one - they were pretty common. It's just a relief dealing with a drum brand when a specific spare might come up more than once every two years and for which I don't have to hostage my family to pay for it - as is the case with Camco.
Drum Palace had nothing and Jollity Farm offered - how do I say this nicely - significantly above market prices.
Am now sorted on the tom arm, which was the difficult one.
