The name says it all Endurance Series Roller Rockers where designed for high endurance racing engines including offshore powerboat race engines. Made of 7000 series aluminum free up valve traim weight. Lower profile desighn allows these rockers to clear stock valve covers and come with short polylocks. Endurance Roller Rockers cam easily handle a 0.950" lift and 950 lbs valve spring. There about 28 grams lighter than Scorpion Race rockers. Micro-polished and anodized.