Replica copies of name brands; name brands like Pazzo, CRG, ASV. The tolerances in machining and metals used may not be up to the same standards. Granted, there are some knock-offs that may have been manufactured to the exact same standards and are a great value, but many are not. Hard to tell what you're getting sometimes.

Had two buddies bought a set of levers each from the same seller. Same brands. Both went on R6's. One caused the brake issue, one did not. It was a track bike so we fixed it with a Dremel. Made the levers look junky, but didn't matter for this application.