Invisible design: F50D2 is an in-ear hearing aid that uses precision acoustic components to provide a sophisticated design that is invisible to wear Advanced sound processing: Adopts 16-channel WDRC digital chip for precise sound processing Excellent sound quality: Enjoy excellent sound quality with 16-channel low-level extension, maximum output tone control and 64-band equalizer Intelligent noise management: Achieve clear conversations with intelligent background noise suppression and adaptive feedback management Convenient adjustment: Easily adjust the volume and switch programs with the multi-function button and volume adjustment key Rechargeable function: Powered by a lithium battery, it provides long use time and a fast 2.5-hour charging time to ensure uninterrupted hearing support Specifications: 90dB output sound pressure level: maximum: 50dB saturated output sound pressure level: maximum: 305dB / average: 285dB Frequency range (Hz): 250~5000Hz Harmonic distortion: 500Hz: 5% / 800Hz: 5% / 1600Hz: 5% Equivalent input noise: Working time: 24 hours Working voltage: DC 3.0~4.2V Charging time: 2.5 hours Battery capacity: 450mAh for charging box, 35mAh for hearing aid Package included: 2 x Hearing Amplifier 1 x Charging Case 1 x Charging Cable 6 x Earplugs 1 x Cleaning Brush 1 x English User Manual