Chastity device discussions and reviews discussion

I’m using the plastic model of that device. I’ve only had it on for a couple of days, but after several hours, the ring feels really uncomfortable under my scrotum. I currently have the largest size fitted. Yesterday, the pain was significant enough to make showering unpleasant. Today, I spotted some minor abrasions forming. Is this typical for plastic? Or should I try an even bigger ring? I plan to buy larger rings anyway, but if a big metal ring works with the plastic tube, would that be better?