This port plug for modular SCUBA valve has left-hand (reverse) threads. It fits Dive Rite brand, Edge/Hog brand, Halcyon brand, Hollis brand, Sea Elite brand, Thermo brand and DGX modular valves. It does NOT fit Blue Steel brand, OMS brand or Sherwood brand valves.

Note that port plugs used on the modular valve with the typical side handwheel are notched on the corners of the wrench flats. The notches indicate the screw threads are reversed, and must be rotated clockwise to remove and rotated counter-clockwise to install. This is the opposite of typical screw threads and attempting to remove the notched plug using counter-clockwise force will permanently damage the valve.