Tee clamps create T shape joints between pipes. Short tee clamps create a T shape join between two pipes, with the clamp slid along and secured in the middle of one pipe, forming the 90° angle of the T branch. Long tees can be used to connect three pipes, two pipes forming the horizontal of the T, and third connected to form the vertical.
Other tee’s in this range allow connections of various angles,crossovers and offsets between two or more pipes.

Much confusion is caused by the sizing and designation of Pipeclamps.
All inch sizes referred to are Nominal Bore sizes and relate to the Nominal {not actual} bore of the pipe or tube used.
For example: The 1" PIPECLAMP will fit a 1" or 25mm Nominal Bore Pipe or tube with an OD of 1 11/32" or 33.7mm.