GM-301 Hearing Aid Rechargeable Sound Amplifier,Spec: Bluetooth Model Blue 1. High-performance noise reduction chip, multi-scene noise reduction processing, high-definition fidelity sound quality 2. Bendable ear wire, ear wire can be adjusted to fit the ear according to different ear shape 3. Using directional transmission, low latency and low lag, in-person chat, telephone communication can achieve natural and smooth communication 4. 360-degree rotating silicone ear hooks, regardless of the left and right ear, long wear without pain 5. Built-in 45 mA lithium battery, continuous use time up to 30 hours 6. Support cell phone BT connection, hands-free calls, high-definition noise reduction (only BT models) 7. Double key minimalist operation, designed for the elderly Parameters: 1. Host battery capacity: 45 mA 2. Battery capacity of charging compartment: 400 mAh 3. Saturation sound pressure level (MAX): less than or equal to 129 +- 3dB 4. Output sound pressure level (average value of high frequency): 120+-4dB 5. Full-range sound gain (high-frequency average): 38+-5dB 6.Frequency response range: not narrower than 500Hz ~4500Hz 7.Monaural hearing aid weight: 5.6g 8.Size: 4.6 x 3.6cm