I just got one of these from MVS. My fist carto tank. I bought them there because you can order them with a variety of cartos. I wanted a 2.0 single coil. I also liked the locking feature. The ring does subtract from the thread length a bit, and when I put it on my ProVari it showed open. I popped in a 510-510 shorty adapter, and its working fine like that. Anyone else here use one of these?