Get a 1.75” Thickwall cylinder. The 2” Flared or 2” Thickwall will be too big for you and will pull your ball sack in, making the experience not very comfortable. I am 5.5” midshalf and it is a great fit. My friend also uses the same size tube and he’s 6-6.25” girth-wise. It’s a better, tighter fit and since it’s thickwall, it digs well into the base.
You should shave your base area, apply a bit of Vaseline, and a hidden secret, use Baby powder right where the ball sack is. This prevents the sack getting pulled into the tube. Very helpful.
Search for Thickwall.uk, they sell thickwall cylinders for reasonable prices. Not cheap, but worth it if you’re into pumping. **Do not go by the suggested size measurement scale you read. Many, including myself, have followed the size guidelines (Vacu-Tech for instance) and ended up with a tube a size larger than what we should have ordered.**
Stick to 1.75”. Anything larger and you’ll regret it.