Here is the description from the Roger Mayer website:
The Red Lion Wah is the latest in our range of wah kits and has been expressly designed to retrofit into an existing Dunlop or Vox wah housing without any soldering. It features continuous variable wah tuning over a wide range that will enable players to easily find their own sweet wah sound very quickly. It is based on our very successful 9090A wah kit and of course the wah sweeps have their roots based on the mods I did for Jimi’s wahs so here in 2002 you can tune into those wah sounds you have already heard with ultimate ease. Only top quality components and magnetics are used and the circuit is very quiet in operation. The flexibility of this replacement card and the performance gained by the incorporation of over 33 years of wah modifications are brought to a head in this card. There are a lot of standard wah pedals without a tuning option and the Red Lion Wah brings this option to players at a very affordable price. Technically the card has a high input impedance low capacitance input circuit which means there is no tone sucking or level loss in bypass mode and there is no need to further modify the standard wiring harness with a DPDT switch as there is no performance to be gained.