There's the Freemax Mesh Pro (Now known as M-Pro I think?) subohm tank, and the less popular Digiflavor Mesh Pro RDA. I assume you're talking about the subohm tank.. I remember something about those coils. There's an o ring that goes on the bottom of the coil heads. Those would fall off inside the packaging, so I had to make sure and inspect them every time.
I hated the top fill method for the M-Pro. Mine used to get bumped open all the time. That would cause the tank to dump out the entirety of it's liquid contents. Same goes for the Fire like 2. I got an older Fiireluke and used the M-Pro coils in that instead.