The NP 02-140 Neckband Headphones for Visitor Guidance and Conference Systems with 3.5mm Stereo Right Angle Connector from Sennheiser come in a pack of 20. Each headphone features a neckband to accommodate additional headgear, such as a helmet, and offers high-quality sound with a frequency response range of 20 Hz to 20 kHz and 32Ω impedance. The single-sided cable allows for easy handling of the headphones and the changeable ear pads ensure comfort and hygiene.