The 3 quarter inch Tee is most commonly used with 3/4 inch rigid pipe and 3/4 inch flexible rigid pipe.
Best to use a plumbing cleaner then pipe cement to assemble. Pipework pushes inside this part.
*White is shown in this picture but part sent out would be grey.*
Internal Diameter: 28 mm
Outer Length: 65 mm
Depth / Diameter: 33 mm