Features:
Classic A circuitry, a flip of the switch gives you up to a 35dB boost.
Supports a maximum input of 18V DC voltage. 
The pedal can also function as a volume limiter.
The sound of the Roll Boost pedal is transparent, and the gain knob fully functional to add some sparkle and a slight boost.
Features True By-Pass Wiring.

Specifications:
Model: JF-38
Color: Yellow
Material: Aluminum alloy
Input impedance: 1Mω
Output impedance: 1Kω
Running current: 2mA
Power: 6F22 9V battery / DC 9V adapter (Neither included)
Item size: 11.7 * 6.7 * 5.1cm / 4.6 * 2.6 * 2.0in
Item weight: 180g / 6.3oz
Package size: 13 * 7.5 * 6.2cm / 5.1 * 2.9 * 2.4in
Package weight: 220g / 7.7oz

Package List: 
1 * Effect Pedal
1 * User Manual (English & Chinese)

Note: 
This unit is without battery, put on the battery by opening the back cover with a screwdriver.