This does the same job as other derailleur hanger gauges, but it looks and feels so much better doing it. im not sure of the artists name who makes these tools for abbey, but i would venture a guess it may be Vulcan himself. The handle is telescopic and extends to double its length, the feeler is stored in the handle. to set the feeler, insert through an eyelet at the end of a screw off cap. tighten the cap to fix the feeler at the correct length, from there you can move the handle independently through its telescopic motion and twist the handle to get the perfect spacing when doing your measurements at different positions around the wheel. this tool has a higher price than most, but as with everything in the bike industry, you get what you pay for. this is an absolutely beautiful tool with the perfect balance of function and form. it has great balance and is nice and heavy. even if you have the park version, this is worth buying. you will be the envy of all your other mechanic friends. and this is a tool that you will have for a lifetime. if you are thinking of getting this, go ahead and do it. you wont regret it and you will be supporting a small craft industry. and while youre at it, pick up the Crombie tool. you cant go wrong with Abbey Bike Tools. I cant sing their praises enough.