I have installed Wilson, C&S and Mueschke ambi's in my guns. The Wilsons required a lot of fitting on the inside, but were good-to-go in terms of finish. The C&S safety was easy to fit, but looked like it had just dropped out of the mold (HOURS of grinding/polishing before it was allowed on my gun). The Mueschke is more like a drop-in part, requiring little fitting, but somewhat loose. I really dislike the appearance of the McCormick part, but it is certainly attractively priced. In order of comfort/function, I would rate: C&S, Wilson hi-ride, old Wilson, stock.