The plug assembly screws into the access fitting body and  seals the bore of the fitting to contain line pressure. Hollow plugs are used  to mount corrosion monitoring devices that require wired connections:  Electrical Resistance (ER), Linear Polarization Resistance (LPR) probes, and  multiple specialized probes.               
                 Hollow Plug:    Overall  length - 5.5"/140mm       Weight - 2  lbs/0.9kg 
                   
 
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