A set of rings for increasing the FPS/Joule output of sniper rifle replicas.
They make it possible to increase the force of the replica by increasing the spring compression in the reload cycle. The rings have different heights, so you can choose the right one or combine several.
Different strength springs have different lengths, too high a ring can prevent the spring from compressing and locking the piston in the rear position.
The inner diameter of the sleeves is 7 mm and the outer diameter is 11.9 mm.

The rings are made with 3D printing technology.