This is the plug ( DHP12 ) that caps the small 1 1/4" "fill" hole used on many acid neutralizing filter tanks.Includes o-ring.
We also have the o-ring available separately ( PN N1024 )
Cross Reference - Pentair part --- CH10746
NOTE: Threaded portion of the plug measures 1 1/2" across.
It's called 1 1/4" because plumbing measurements are always the inner most "depth" of the Thread area, and not the "outer" diameter of the Threads.
Also, you'll notice it fits in a hole in tank that measures about 1 3/4" across.
** Current = From outside of thread to outside of thread is 1-5/8 and It's overall depth is the same1-5/8