Basically: ONLY BUY NEW AND SEALED CAR RECEIVER DRIERS
Used car receiver driers keep coming up for sale in listings, These are no good, totally useless in fact. As soon as they are removed from the car they start absorbing moisture in the form of water vapor from the atmosphere. This floods the desiccants inside the unit quickly overwhelming the units ability to dry the refrigerant, an iriversable effect. Receivers are a filter just like any other and you would not fit a used oil or air filter would you?
The same really, in someways, applies to all Air Conditioning components available second hand. Condensors will need to be flushed with an appropriate AC approved flushing solution, have a vacuum pulled ideally to 29.92 (in.Hg) at sea level and be able to hold that vacuum for at least 45mins before being presure checked with for example OFN (Oxegen Free Nitrogen). Compressors proberbly have dried out seals from lack of use and the Expansion Valves (where fitted) are most likely clogged with all manner of rubbish.
By all means purchase any Air con part second hand but be aware that Compressors need overhauling and Condensors at the very least will need combing and cleaning.
But please don't waste your money on used Reciever Driers, Accumulators, Orifice valves or Expansion valves. It will cost you more than you save in the long run.