This upgrade kit will fit the Echo1 ASR, UTG L96, and APS2 Clones. The Upgrade kit includes a metal piston and spring guide with bearing, as well as an upgraded spring.
The bearing on the metal spring guide reduces twisting friciton from the spring and lets it compress and expand smoothly.
The upgraded spring should produce just over 500fps when installed in the Echo1 ASR or other compatible rifles.
When upgrading the main spring in bolt action rifles upgrading the sears and or trigger pack to handle the additional stress is highly reccomended.