Njoy has a great understanding of anal anatomy and how butts behave! :) The Pure Plugs have enough space for the anal sphincters to close around comfortably. Pair this with a gentle curve that follows the natural curve of the rectum and you've got one hell of a plug!! The base of the plug sits nicely in between the butt cheeks.
I find the Pure Plug 2.0 stays in well and is quite comfortable for extended wear. The stainless steel is nice and slippery with only a small amount lube (hooray! I get to use silicone lube on this toy). My favorite butt plug thus far!