What chastity ring diameter size are you using?

Regarding the first question, it's usually 45mm for me. Although the 'Cherry Keeper' ring which is this exact diameter does get uncomfortable admittedly, more so than metal ones.

I don't feel comfortable wearing a device 24/7. In the summer months, I can get away with a 40mm ring as long as the gap is wider than that of the A231. In Winter, I have to use the 45mm ring as they get tight/scrunched up. Sometimes I have to take it off to relieve the burning sensation.

I even think about getting a 48mm or large ring at times, but if I was going to go custom with a hefty price tag, it would be around 1/771 inches.

Switching from devices like the CB6000s, Birdlocked and 'Ridem Tiger' devices to smaller cheap Chinese open devices certainly helped improve blood flow, and minimising any potential nerve damage, along with improving overall comfort, for a fraction of the price.