A what? L
The compressor for an air conditioner. I believe R4 may actually be the compressor model rather than the refrigerant it's designed to work with, but I'm far from certain.My understanding is that you can't replace the seal without first draining the refrigerant from the system and later replacing it with the correct mixture... and that this may require both special equipment and licensing. But I may be completely wrong.
Not really "user serviceable" are they? L