New upgrade spring for bolt action sniper rifles.
Made of steel spring wire, blackening surface, thermal tratment.
Ends of the spring are grounded in.
Older AirsoftPro springs where little bit "over scaled".
These new springs better match to its nominal value.
Please note this is upgrade spring with the outer diameter 12,8mm and inner diameter 9mm. It is suitable for upgraded pistons which larger inner diameter !