Feature:1. High Quality Material: The transmitter and receiver are all metal shells, which are sturdy and durable to ensure a long service life.2. Unlimited Use: The monitoring system can use unlimited number of S3 receivers under the same frequency.3. Portable: The compact body pack receiver is easy to be tied to a belt or guitar strap, which is light and practical without burden.4. Easy to Use: No complicated menus, only simple volume and mixing control buttons, three receiving modes: mixing, stereo, and mono.5. Clear: The signal to noise ratio of up to 90 dB can provide clear and complete sound at any volume, reliable radio frequency connection coverage up to 100m.Specification:Item Type: Wireless Earbud Monitor SystemMaterial: Iron ShellFrequency Range: 626-662MHzHeadphone Output Interface: 3.5mm Stereo JackTransmitter Power Supply: DC12V/300mAReceiver Working Time: More Than 12 HoursReceiver Battery: 2 x AA Batteries (Not Included)Operating Range: 100m (Open Environment without Obstruction)RF Transmit Power: <10nWDynamic Range: 90dBHarmonic Distortion: <1% (1KHz, 20KHz Frequency Deviation)Frequency Response: 40Hz-18KHzHeadphone Output Power: 65m (32 Ohm)Voltage: 110-240V.Package List:1 x S3 Transmitter1 x S3 Receiver1 x Power Adapter1 x Manual 1 x Antenna2 Pairs x Ear Caps1 x Headphone1 x Battery BoxNote:Each frequency band can use up to 8 sets of wireless monitoring systems at the same time.