Mercedes: Gasket, model chassis, maternal grandmother

Question
I'm trying to find out what do I need to ask for when I call the dealership about a specific part.  What I'm looking for is a gasket that is suppose to go the hose that connects to my air conditioner.

Answer
Monique,
They will probably want the maiden name of your maternal grandmother... just kidding..
Year model Chassis series  124 body style, 420sel etc. Engine type V8 four cylinder, automatic or strait drive. gas or diesel etc.
Which hose suction or pressure. Which end firewall or back of the compressor.
Also is the system is R12 or 134A. Vehicle Identification Number(VIN) will also assist in the search. The VIN will be on a data plate in front of the dash under the windshield in many cases on the driver side.
The dealer price will be considerably higher that aftermarket.
So, what are the symptoms of your problem?
Good Luck
Rob