... in USA,EU,Indonesia,Brazil,Austrilia. 3.Excellent quality. spark plug c7hsa1. Multi-ribs of insulator eliminate ... sealBolt Part Heating,Low Combination Between Sealant,Low Seal PerformanceHeating combination by sintering furnace,stable quality control,high seal ... 35KV high voltage test,high insulation perfomanceWhole AssemblyPoor quality stabilityLarge current hot state seal,high seal ...