In 1971, Mike Matthews' Big Muff Pi sparked a revolution in fuzz. Thick, creamy, and sustaining, but well-behaved and more amp-like rather than buzzy.
The Skreddy 1971 pedal combines the same elements of the early "triangle knob" BMP, like carbon comp resistors, ceramic capacitors, and 2N5133* transistors, into a design that has its gain pulled back just a bit. This allows the distortion to retain a balance of tightness and openness and an even more amp-like feel as opposed to an overwhelming liquid fuzz character.
The effect is positively addictive! And hard to classify exactly. It's not an all-out fuzz so much as a distortion reminiscent of a cranked Laney or Mesa Boogie with plenty of sustain and a very chord-friendly gain structure.