Rocker Cover Wing Nut SetsThese are a chrome set of 4 Wing nut for rocker covers valve covers extenders great for the easy reach of otherwise damn hard to get at number that hold down the early side mount rocker covers. There are differences in the thread types that screw into the heads.. Some heads have different thread sizes.. Most Chevy are all 1 4 20 in thread with height of 4. 25 or 5 inches .. Most Pontiac and Olds engines are larger with 5 16. Choose the size you need