Threaded injection point Tee piece.
Select physical thread size. (Note: Pipe thread sizes can be confusing... 3/4" or 20mm thread phiysical size is 1" or 25mm)
So, if you want a 1" (physical size) threaded Tee, order the 3/4" (20mm)
Select pipe size...
(40mm pipe measures 48mm OD & 50mm pipe measures 60mm OD)