Sizing the Ring for a Mamba Cage Clone

I’m currently using a plastic Mamba clone that feels like the most comfortable and sensible cage option for me. It’s not flawless though, and I recently spotted a Mamba V6 with a contoured ring that seems ideal.

It claims:

“the Mamba shape helps reduce erection strength and duration by allowing the deep dorsal vein and the superficial dorsal vein to do their work.”

The issue is that the available ring sizes differ from what I’m used to, so any guidance would be helpful.

I typically use 40mm rings. The one I have now is 43mm; there’s a noticeable gap when I am cold and flaccid, making it easy to slip out (though this has always been an issue for me, I’d prefer it to stay in place better). I’ve also worn a 38mm hinged ring before, but sometimes the pressure during erections caused pain in my groin area as if blood flow were being restricted too much.

So, would a 38mm ring with this new design work for me, or should I stick with the 43mm one? Link to product: