what sized ring should i choose for the holy trainer 2

I went to a hardware store and picked up several round steel welded rings in different sizes to test. A 40mm round welded steel ring is too small for me; I cannot get inside it at all. However, a 45mm round welded steel ring fits. One night while lying down, the lubrication allowed me to slip out of the 45mm ring. What size Holy Trainer ring would you recommend I purchase? Thank you

I've worn my Holy Trainer for just under a week now. The break-in period has been very good. There is some pressure on the top of the shaft, but nothing serious. I'm using a 45mm ring with the small cage. My flaccid length is about 2.5 inches, and the combination of cage and ring works well for me. The ring feels tight but not overly so. Good luck