I've posted this before on LS, but one night while googling something else, I came across some good info about Redmax. Back when Stihl was getting close to final development of the 4 mix engines, they bought 100K of Redmax's strato engines, but then shelved them when it looked like going ahead with the 4 mix would be the way to go based on what the EPA was telling the various manu's. They are now using them up in the newer BP's and probably these new trimmers as well. I should have kept a link to the article. It was really in depth about what all RM has been involved with.