Just as a matter of interest - what are the ring size for the CB6000 you mostly use. There is multiple choice if you vary the size. Probably like many, I only use two of the rings and have just had my "normal" ring break on me and have had to send for a new one, post haste! The support from Mr Miller in the US has been great - not so the retailer in the UK. Happy to sell me a new one - but slow to respond to my requests to replace the 3 month old broken one so far. No response to emails or messages when buying the replacement. (Update - vendor responds asking me to send broken bits to request replacement from States.) it might be an interesting piece of research - unless already done.