Califone 1214AVP-01 is a basic classroom listening center that provides flexibility to expand existing lab systems. It includes two 1214AVPY 4-position monaural jack boxes with silver-plated contacts for a solid connection and moisture resistance. Each jack box has individual volume controls and durable ABS plastic housing. The package also comes with eight monaural 2924AVP headphones with 40mm diameter speakers, mylar diaphragms, and ferrite magnets. The headphones have a frequency response of 40 H - 18 kHz and a sound pressure level of 93 db +/- 3 dB.