The retrofit works on fuzz pedals, as well as other dist/overdrive applications. I used to use my old WOF wah on amp overdrive + a Keeley MT-2 and Keeley DS-1 and the 'wah' sound would always get lost. I emailed Geoffrey Teese and he was saying how the Foxrox takes care of the problem. I considered A fulltone Clyde deluxe and an RMC 3, before settling on a picture wah. I would say stick with a Teese wah - the guy lives and breathes WAH and has always been helpful to me if I had any questions. Fulltone on the other hand, don't specialise solely on wah pedals and great customer service.