This is for a set of 5 seals 1 set for a Yamaha 660 cylinder head all years raptor grizzly rhino. They are high performance viton seals that reduces friction & creates a better seal on the stem. These are designed to have optimum fitment and give maximum life. They are resistant to high temperatures, petroleum products and corrosive acicdic gasses that are by product from combustion proceess. These seal retain there ability to seal in situations where others harden and let oil enter the combustion chamber causing carbon build up, detonation, and loss of power. Best you can buy at the best prices. Same seals we use on our high performance race heads.