I have a Sig M11-A1 they take 229-1 mags. Will Legacy frame 229 15 round mags work in my M11-A1 ? thanks for the help

The short answer is yes.

Here is the long answer. SIG standardized the 9mm P229 frame with the .40/.357 P229 frame in late 2009. Since this frame has a wider mag well than the original P229(9) frame, they designed the new 9mm mag for it, which has the wider body at the bottom half, which they dubbed 229-1. The old mag will work in the newer frame, but since it's a little skinnier, will wobble slightly more compared to the 229-1 mag in the same frame.

Note: The majority of folks will have no issues using the old mag in the newer frame, although some do. I know at least one member on here had problem with reliability.

Note #2: Never buy the 229-1 (aka E2) mag for the old frame. It will not fit in.

thank you for the response