They have a large magnet that slides over a standpipe and is retained by the top nut. After that, there is a small spring, valve, and valve seat. Not much to them at all. The only difference on the new ones is they have a small filter in the secondary top nut to keep dirt out of the valve seat.I have not, but ARBs are going in this one, so I'll be sure to do a practice tear down when I set the system up.
