I use a loose ring KK ultra for George, I have a drawer full of bits that we didn't get on with - I could of bought the bit new in the first place and saved money if I hadn't tried lots of other things! It would certainly be a good idea to try one first from a bit bank - maybe there is one on the HHO bit bank? I got mine 2nd hand from our local shop so a bit less than full price.
you could take it on a month's trial with shop4bits for £5, then if you think it's worth the money, pay the rest or send it back and only pay a £5. I do this with all my 'expensive' bits.