... porcelain insulatorStructure: L With CT is available, 1,2,3means different length for installing CTAnti-pollutior type ... at the end), none for normal type . 1,2,3means design serial number Additional performance code : ... min. creepage is 25mm/kV, heavy pollution area 4 the min. creepage is 31mm/kV, extra heacyOperation ... extreme contamination and salt fog area 4.5KV Air To Oil Transformer Bushing