If your rifle is low in power or becoming inaccurate due to inconsistency with power, it could be because air is escaping past the piston seal in the compression chamber. This replacement part with help rectify the problem. It is also worth while replacing the breech washer at the same time.
This is a replacement Piston head seal for the Stoeger X20 air rifle models.Please note, sometimes design changes during production, please ensure you require this seal which is the 25.5mm outer diameter version.