When a branch is larger than the other two run openings, it is referred to as a bullhead tee. On a "bullhead tee" the side outlet is the largest socket on the tee and the side outlet is referred to as the "bullhead". Thus, Bullhead Tees are the tees in which the ports of the run are smaller than the port of the branch.

In general, the specifications for a fitting indicate the sizes for both ends of the run first, followed by the size of the branch. In the case of run openings being different sizes, the larger run opening would be listed first. In similar fashion, if there are two branches of differing sizes, the larger branch opening would be listed before the smaller branch opening. But in all cases, branches are always listed after run openings.

Tees are always labeled as "N x N x N TEE with the side outlet as the last size. The larger of the two sockets is always listed first. Thus a 1 x ¾ x 1/2 TEE SST has a 1/2" threaded side outlet (T for threaded) with the remaining sockets being 1" and 3/4" solvent weld sockets (SS for slip, slip).

90º Bullhead Tee is best used in Low Pressure Heating and Air Conditioning Systems. For Dust Collection Systems, Lateral and Boot Tees are used. Boot Tee is commonly used in confined area that does not allow use of 45° Lateral Tee.