Warm and Full Humbucking Sound Low Profile Design No Battery Required Allows Temporary Installation with No Modification NEO-D SOUNDHOLE PICKUP FEATURES: Neodymium magnet structure for exceptional string balance and sparkling acoustic clarity Low profile, hHigh-impedance design needs no battery Easy installation with no alteration, plug and play right out of the box Excellent string-to-string balance and acoustic clarity Fits in soundholes as small as 3-7/8″ (98.5 mm) diameter Humbucking model features stacked coils to eliminate noise