If your interested in the micro rings and nothing else you could go for the longer tubes called trumpet tubes, these I believe are a little better than the micro rings. These can be purchased from the USA direct, I can give you details of websites if your interested. I havent seen these available in the UK as yet.
'Shrinkies' 'shrink-links' 'shrink tubes' everyone has a name for them but I call them shrinkies. I do more of this method on my clients than any other, but it does depend on which shrinkies you use, there are different ones on the market, some have no adhesive lining and have a thinner outer wall than the adhesive lined ones.
I suppose it depends on which install you prefer but do your research first and then make your decision.