Baltimore Sonic Research Institute GFZ - UsedThe BSRI GFZ blurs the lines of distortion and fuzz. The circuitry uses complementary metal oxide semiconductor (CMOS) inverters to produce a wide range of distorted textures. The controls interact with each other to create wildly unpredictable sonic results. This Baltimore Sonic Research Institute GFZ is in very good condition and is fully functional. There is Velcro on the back plate.