In the words of MXR:

Now in an MXR mini housing, the Classic 108 Fuzz gives you all
the same vintage fuzz tones in a much smaller footprint. Like its
larger predecessor, its loaded with the silicon BC-108 transistor for a
round and dirty crunch. This Classic 108 Fuzz also has the same
no-nonsense control interfacejust crank the Volume and Fuzz controls to
your liking and start riffing. Use the Buffer switch on the side to
make the fuzz play nice with wah pedals.