I did not replace the receiver/drier. Some idiot (me) put a hole in the evaporator coil when I was replacing the heater core, so my 29 year old car with working a/c lost it's entire charge. I found a good used coil, and replaced it and the o-rings only. I did evacuate the system with a vacuum pump before recharging it. So far, so good - I'm getting about 60-65 degrees at the vent on a 90 degree day - hopefully it stays that way!