Features: Sound hole installation, no need drill hole, easy to install. The preamplifier is suitable for mounting on guitars with sound hole diameter during 95~110mm. Cork pad clamp design, no damage to paint of instrument. It is a pickup that can be operated on your mobile phone (download the free APP: Double+). It has various DSP effects, including compress, reverberation, chorus and delay. It supports active recording, wireless output, BT audio, really a magical preamp. With wireless transmission mode, thus you can connect the amplifier through the wireless receiver. Comes with a wireless receiver for wireless output, you can connect guitar to amplifier without cable. Receiver with 1/4" audio plug, it can be connected to AMP or audio controller. Support 2 different sets of BT transmissions at the same time. DOUBLE G0 PRO LE for connect for APP, and it you want to input some beats or accompaniment via BT device, connect it to the DOUBLE G0 PRO. With record and preserve music function, just connect your device with a suitable cable to the 3.5mm active recording output jack(4 channels). Both of preamp and receiver are powered by built-in polymer lithium battery. Battery is rechargeable, large capacity, long life and has stable performance. Equipped with a nano gel pad, which is washable and reusable, convenient to use anywhere. Specifications: Material: ABS+PCB APP: Double+ Battery: 2000mAh Item Size: 103 * 68 * 50mm / 4.06 * 2.68 * 1.97in Item Weight: 159g / 5.63oz Package Weight: 534g / 18.83oz Package Size: 17.5 * 15.2 * 5.5cm / 6.89 * 5.98 * 2.17in Package List: 1 * Pickup 1 * Receiver 1 * Nano Gel Pad 1 * Tail Nail Leather Cover 1 * Output Tail Nail 1 * Vibrating Horn 1 * Screwdriver 2 * Cable 2 * Clip 2 * Gasket 1 * Manual (English) Note: This product is a magnetic coil and microphone combination pickup, which is suitable for all steel string guitars, but not for all nylon string guitars.