The Alpine concentric vent termination kit is an optional accessory for use with furnaces of 90% AFUE or higher (furnaces requiring PVC vent piping). The kit makes it possible to use the optimal two-pipe installation for these furnaces while only cutting one hole through the wall or roof. Instead of a separate hole for the exhaust pipe and a separate hole for the combustion air intake pipe, this kit merges the two pipes into a single concentric vent pipe which passes through the wall or roof. A specially designed rain cap draws combustion air in from one direction while directing exhaust in another direction. Select the concentric vent termination kit that matches the vent size required for your furnace. Please note in the specifications listed below that the actual diameter of the pipe going through the wall or roof will be larger than two or three inches respectively.