This is a new reproduction flexible rubber seal for the evaporator lines to housing on 1973-79 Ford Trucks. This is the version that seals the housing the engine compartment. All AC trucks have this type of seal, and the original is almost always brittle and cracked. Note that this version has one 1/2" diameter hole and one 3/4" diameter hole, and the holes are diagonally spaced. Some earlier evaporators had both tubes 1/2" size, and holes placed different- and this won't fit well for those even though they look similar. Please look at your evaporator housing before ordering 

These are high quality rubber that will last for years. They are very flexible, yet durable.