14mm X 15mm M22 Twist Seal Plug is meant to convert a 14mm stem to a 15mm stem of a twist seal coupler. This is commonly used when installing MTM Hydro Spray Guns onto a Sunjoe, AR, Ryobi, or Greenworks pressure washers that require a 15mm conversion. 14mm and 15mm refers to the Inner Diameter (ID) of this M22 fitting. When installing the 15mm side into a 15mm coupler, it will be tight but it will fit!.