I've reached 2" with a softer jelly type plug, but I want to go further. I bought a 2.25" plug seeing where as that seems like the next logical step, but no matter what it doesn't seem like it's ever going in. It's glass though, so that might be part of the problem. Lube doesn't stick to it as well as glass is a near frictionless surface. Should I stay at the same diameter and simply switch materials?