Ultimate Ears Pro Line Drive, Line Level Signal EQ Booster, Can be connected to line outputs or headphone outputs, Switchable between signal source and in-ear monitor (IEM), Enables consistent fidelity and reproduction of any IEM sound signature, regardless of audio source, whether it is connected to a mixing console, in-ear monitor (IEM) or headphone output, Input/Output: Mini-jack, Dimensions: 50 x 55 x 20 mm, Weight: Approx. 500 g, Includes 2 extra lithium battery (CR2450 3V) and 3.5 mm stereo input cable