This is an original e-earphone model that is compatible with earphones and headphones with various impedances, and pursues ease of use by using only AAA batteries. Gain can be switched with internal jumper pins. The orange side panels are pretty neat.
Accessories: instruction manual
Main specifications: 1 headphone output (3.5 mm stereo mini), 1 analog input (3.5 mm stereo mini), compatible impedance: 8 to 300 ohms (when low gain) /16 to 600 ohms (when high gain)