FX website shows that the material should be Polyurethane 70 shore. The original O ring blew away in just 100 shots. Now the options are Polyurethane 70 shore and 90 shore. I have got both but 90 shore is too hard and I feel that when the JSB pellet passes through the seal, its skirt gets smaller which affects accuracy. While 70 shore is softer and the skirt remains safe which translates into better accuracy. What I feel is that if the seal is on the pellet probe then 90 shore is fine but if seal is inside the transfer port then 70 shore is better. Please share your experiences in this respect. Specially in the case of FX .22 pcp.