Junk. I bought 2 at a gun show. One malfunctioned at the range. The spring got hung up inside the mag well and the rounds were bouncing around inside. I threw both in the trash. Never again.
I tried them because I wanted range spares and they came in 10 rd capacity. They function fine for me. I think the negative was my set doesn't always lock the slide after the last round. If I could do 10 in s+w mags I would. I used magguts in my s+w and each one now has plus one without any further extension.