For the same reason I have used rockers, push rods/retainers, cam and these 16 lifters they didn't fail plus their America made not Chinese.. If one of them would've failed all 16 would have been in the dumpster.Why would you hang on to them as most people would install new ones when rebuilding an engine to avoid having to replace them if one isn't working correctly. As far as comparison, the 396/427 should be the same, but the earlier 409 might use a different version but don't quote me on it.