This is a new reproduction flexible rubber seal for the evaporator lines to housing on 1973-75 Ford Trucks. All AC trucks have this seal, and the original is almost always brittle and cracked. Note that this version has two 1/2" diameter holes. Later evaporators had one tube that was larger and this won't fit well for those even though they look similar. 
These are high quality rubber that will last for years. They are very flexible, yet durable.