Tees are named first by the size of the ends, and then by the size of the middle connection (typically called end-end-middle). The order of the ends does not matter; for example, a 1/2" x 3/4" x 1/2" tee would function the same as a 3/4" x 1/2" x 1/2" tee if you just flip it around. If a tee only has one size listed, all three connections are for the same size pipe.
Brass tees, copper tees, black tees, and PEX tees can all be found at www.supplyhouse.com
