9" of john holmes is the best can do. It. Just. Doesn't . Want. To go in.
I have been going for girth all of these years. I have vowed to myself to stop at 2 - 3/4 thick. One of the annoying things about that is the thicker they are, usually the longer they are. I love the idea of feeling the balls against my ass but just can't get anything longer than 7 - 1/2 inches in me. Frankly I'm nervous about going that deep. I recently got a thinner longer dildo to train with but I just can't get past that second wall.
6 inches easy
Longest I've taken is 14" of an 18" double ended we have, thickest I've taken is a monster 8" circ. - that's 11" insertable.
My 50cm plug is the longest, all the way to the suction cup, and OMG! I've worn it that way a few times, but just playing in the shower is awesome.
13 dildo and a 24 inch that is thing at the tip and then get thicker at the end. Base is like a butt plug with a suction base.
My go to is 6 1/2 insertible and about 1 1/2 wide. When I am in the mood I dp that with a 5" long and just over an inch wide dildo. That gives me a great stretch! Then I have a narrow 7 1/2 long toy that breaches my sigmoid colon for a great feeling!