I dont know who machined these for them, but they are not a quality part...I spent hours upon hours trying to thread the provided bolts down through and into the head.....piss poor machining at best...uneven flanges at the end made it a total nightmare for install, countless hours, grinding sockets, cutting allen wrenches, lotsa screwing around...and the sad part is they will probably leak like bp oil spill, havent got that far yet....I WOULD NOT RECOMMEND THESE COVERS WHATSOEVER.....