XNBR Carboxylated nitrile rubber is an improved version of NBR type rubber, XNBR combines the technical properties of nitrile rubber NBR but with an increased strength, higher abrasion resistance and a tolerance to chemical additives which are used in fork oils.
Had these seals on my ducati 1198s for nearly 8000 miles (including 2 track w/ends in Spain,where they got a proper workout) before they leaked. Nearly twice as long as original ohlins seals lasted.
No issues with stiction. Great product.