White ring around penis where the rubber meets the cylinder - Soma

[thegreycat]

Hi
I've been using the B Cylinder for a couple of weeks now, and after my sessions I have a prominent red "ring" around the lower portion of my shaft where the rubber insert meets the mouth of the actual cylinder. It's as if there is the tiniest gap between the rubber insert and the start of the B cylinder and the pressure is causing the skin to pinch? There's no pain or discomfort.

Usually this goes away after a short period of time, however yesterday this ring has turned white and has remained on the skin. I have stopped using the VED for the time being.
Just wondering if there are any tips from fellow SOMA users on getting a better fit? I make sure the rubber insert is as fully inserted as it can be... I do not get this with the A Cylinder.
Thanks