KnockBlock G4+ (KNB)The G4+ KnockBlock is an essential tool for tuning and can aid in the early detection of incorrect ignition timing, lean air fuel mixtures and mechanical issues. It is used it with ear buds, headphones or noise cancelling ear muffs and features special filtering to allow you to listen in and detect knock early. Listen to one or two knock sensors Special filtering design improves signal to noise ratio Can be used with ear buds, headphones or noise