My Coil-Rite set didn't come with this sort of disk. It could be to protect the bag from sharp edges on the spring perches - in which case it could be needed on either end but apparently is needed on neither - or it could just be a spacer to fit the bag length to the space (which is what the Firestone rep suggested when I called). I don't see any connection to the hose fitting. Whatever the reason, with my kit in my Sienna is apparently is not required.DTJ9610 said:I ran the nozzel out the top of the coil. However I place the disk at the bottom thinking it was there for support. Do I need to swith this to the top?