My evo was not quite performing, not enough to warrant a new spring though as it was only a few fps as I wanted to get the maximum potential out of it, so I had a look around and no one seemed to be selling adjuster rings for it, so we decided to make our own.

The set comes with 1,2,3,5,10,12.5, and 15mm 3D printed fps adjuster rings.

I run a combo of these in my evo and they work brilliantly