From 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, it’s loaded with the silicon BC-108 transistor for a round and dirty crunch. This Classic 108 Fuzz also has the same no-nonsense control interface—just 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.

Input Impedance / Buffer Switch On: 800 kΩ
Output Impedance / Buffer Switch Off: 10 kΩ
Output Impedance @ 1 KHz, Maximum Volume: ~16 K ohm
Output Impedance @ 1 KHz, -6dB Volume: ~120 K ohm
Maximum Output Level: -4 dBV
Maximum Gain @ 1 KHz, Volume & Fuzz Max: 55 dB typ
Bypass: True Hardwire
Power Requirements: 2.5 ma @ 9VDC (not included)