Bought it for my CA M15A4C to use it with my CIRAS sling. It doesn't fit. I mean it fits but doesn't sit tight in its place as the original plastic part does. The only thing I managed to do is to fix it as hard as possible with a stock pipe.
By the way the steel the sling is made of is of poor quality - it is too soft and I'm pretty sure it would cover with rust after the first time being wet. Recommended to paint it, or, better to choose something else.