Our Leather Seal Replacement threads direct into the piston. The thread is commonly an 5m x 1m in most Leather Seal attachments. If the thread is different from the one we supply, the OEM screw that is currently in the Leather Seal may be put through the hole of the seal retainer and used. Either way, there is now an option to use synthetic sealing to greatly improve shot cycle and velocity performance. Vortek Vac-Seal 26 adapter, also includes a Vac-Seal 26 piston seal. This adapter / upgrade is designed primarily for 26mm cylinder Weihrauch airguns with leather piston seal mounted. With this Vac-Seal 26 synthetic upgrade you obtain significantly better performance and smoother operation, and significantly more damping against piston slam. Easily installed with a standard Allen key. VORTEK Vac-Seal also prevents spring fracture, which is commonly found on older spring rifles with leather piston seal.