... tube has got the TUV certification of German and SGS certification, satisfy the ROHS standard. ZM55 2R ... from 75V to 500V.Norminal D.C Spark-over voltage includes 75V,90V,150V,230V,350V,420V, ... ±0.2mmNominal .D.C spark-over voltage350VVTolerance of VS±20%Impluse spark-over voltage at 1KV/ μs≤900VImpluse ... voltage135 VDC ZM55 2R350Lgas discharge tube protection and over-voltage protection