a, factory direct sales, good quality at low price b, loud and clear sound, less noise c, long wire which is easy to ... hearing aid,hearing amplifier device:1. much cheaper price,good sound quality2.max level 128db,helps to hearing lound and clear3 ... .very nice amplfier to make sonic hearing aid SpecificationMaximum Saturation Sound Pressure Level( SPL): 128dBMaximum Acoustic Gain: 71dBSound Verity:< 8% ...