These EMPTY resin / media tanks are the most commonly used sizes.
Industry Standard 2 1/2" x 8" NPT Opening
Used by Fleck, Autotrol, Erie, Rainsoft and many other brands of control valves.
Replacement tanks for Park International, Structural Fiber, and other Brands ( but NOT Uniflex or any other NON-Threaded tank ).
NSF Approved Clack ( Wave Syber ), Structural and Enpress Tanks ( depending on size / color which brand will be shipped ).
For Water Softeners, Iron Filters and Carbon Filters
Tank Diameter - How To Measure and Why
NOTE: Almond should not be used Outdoors, and Black is recommended instead.
Blue and Gray also available in some sizes, by Special Request.** Tanks are called 2 1/2" x 8 NPT opening, but it Looks more like 2 3/4" but it's still CALLED 2 1/2" ( THE INDUSTRY STANDARD ).
The 2 1/2" is the inner pipe thread depth, and not the OPENING of the Tank.