EZ-FLO 42035 Clean-Out Plug with Countersunk Head, 4 inch, Brass

Eastman 4 Inch Cast Brass Cleanout Plug, Countersunk Design for Flush Fit, 42035

Camco RhinoFLEX 6-in-1 RV Sewer Wrench | Compatible with 3-Inch and 4-Inch Male or Female Sewer Clean-out Plugs, Slotted or Flush Sewer Plugs, and All 4-in-1 Adapters (39755)

Canplas 193064 Flush Cleanout Plug, 4-Inch