I previously purchased one of these tools from Wood Workers Workshop , but the owner has apparently retired and passed his business on ( see
http://www.woodworkersworkshop.co.uk/ ) to
http://peterseftontoolshop.com/epages/e ... orkshop%22 and they DO sell replacement cutters.
(They also sell the Router Raizer, which I found to be an excellent addition to my Dewalt router in a Bench Dog table.)
As regards function, they are very easy to use - as the US website explains, they were designed by a metalworker, and work in a similar way to metal turning tools. Very good for giving confidence to novice turners, as there is no 'first get the bevel rubbing on the workpiece . . . .' - just set the bar flat on the rest and poke the tool into the wood!