This is the same version that Billy Corgan owns and used on Siamese Dream. 4 Big Muff which has the same IC driven circuit as v. 5 but minus the Tone Bypass Switch. Needless to say these sound amazing and are a bit harder to come by than the more often seen Tone Bypass version. If you have any questions feel free to ask and please check out my other listings.The item "Electro Harmonix Op Amp Big Muff v. 4 1977 Vintage Fuzz Pedal EHX" is in sale since Saturday, March 9, 2019. This item is in the category "Musical Instruments\Guitars & Basses\Parts & Accessories\Effects Pedals\Fuzz". The seller is "77superbass" and is located in Glasgow. This item can be shipped to European Union member countries.