For sale/wanted (Please be aware of scams) discussion

I picked up a black HT v3 last week. Being new to this, I used the string method to gauge the ring size when placing my order. It looked like 40 mm would do the job while 36 mm might be too tight. After wearing it for several days, I saw that the whole assembly rotates and one of the balls can slip out quite painfully! I reckon I should track down a 36mm ring to see how well the device wears with that size. Thanks!