Manley valve spring cups are designed to protect your expensive aluminum cylinder heads from being galled by your high pressure valve springs. There machined to .062" thickness from heat treated steel with a corrosion resistant black oxide finish and are designed to work with 1.550" O.D. dia. valve springs. Manley valve spring cups are sold in sets of sixteen and the racer must choose what I.D. they need for the valve spring seat clearance. Spring cups have a O.D. of 1.680".