What you have pictured is a "brass reg seat housing", not a piston. The actual pistons are very different make sure you tell Dye the right thing when you order one.
They can be used in either reg the difference is in the length. All that affects is the adjustment range, not exactly pressure but how far and how sensitive the adjustments are.
Just be sure to test the output pressure before installing it on a gun, you should be fine.
Did you loose one? Or is yours destroyed? The rubber tip is replaceable if that's all that's wrong.
Either way I have lots here at the shop in various lengths I can send you.
Measure yours if you have it and PM me if you can't find one.