These are federal mogul 273 pistons thank you all for your input but I've decided to go with a 318 instead,your all right as far as shipping,machining costs go it's tooooo much trouble, I know the egge L2221,2bbl pistons and L2222,4bbl pistons are already machined for the locks but weight a ton!!! (L2222's with pins= 652 grams!!!) and the cost factor to build a 273 isn't worth it,thank you all again.