Charging System Tester / Pack Size:1Rotary 9074, Prime Line 7-05948, Foley/Belsaw 5977164, Green Line 62480, Laser L6039, Laser 97381, JThomas JT-1198, NHC 288-5911, Napa 7-05948 Checks both 6 and 12 systems, Test once with engine running and a second time with engine off and starter cranking, Bright light emitting diodes will tell exact condition of battery and capability of charging system, Five voltage ranges, Can also be used to check plug-in battery chargers