Morris 21892 Service Insulator Wire Holder, Lag Type, 1/4" x 1-11/16" Porcelain Wireholders - Electrician's Porcelain Head Wire Holder. Indoor or Outdoor use in Overhead Service Entrance Service Insulator Wire Holder has Porcelain head on lag screw These small ceramic insulators can also be used with all fence wire including high tensile, poly rope, and poly tape 600Volts Max