Bowens has a three-lug fitting, and is somewhat close to the *generic* mount used by a number of Chinese-made monolights, like JTL for example.
I have an inexpensive
eBay softbox that uses basically the SAME speed ring you show in your post, and I needed to file down the lugs on the JTL monolight just a tiny bit to fit the speed ring.
I'm not sure about your question, but the 7 inch reflector needs to be removed, and then the softbox and attached speed ring is mounted to the monolight's mounting ring.
EDIT: I did a quick bit of research, and found the Mettle monolights,sold by the OECamera
eBay vendor out of League City, Texas which coincidentally, is a vendor I have used,and I can see that the Mettle monolights use the Bowens style 3-lug pattern; be aware that the "fit" of the speedring I got with a sotbox from that same vendor was not quite up to the engineering precision one would hope, and it required me to file out the receiving lugs on the monolight in order to fit the speed ring into the monolight; while the Bowens 3-lug pattern is simple, it seems that some Chinese firms are pretty sloppy with the measuring and manufacturing on those softbox speed rings and/or the monolight makers are not following the Bowens 3-lug pattern precisely. At the price of this stuff however, one ought not be surprised that high precision engineering and manufacturing has not been provided.