... tube has got the TUV certification of German and SGS certification, satisfy the ROHS standard. ZM55 2R ... 75V to 500V.Norminal D.C Spark-over voltage includes 75V,90V,150V,230V,350V,420V,500VModelGas ... spark-over voltage350VVTolerance of VS±20%Impluse spark-over voltage at 1KV/ μs≤900VImpluse discharge current (Wave ... VDC ZM55 2R350Lgas discharge tube protection and over-voltage protection