These are for the XS 79 models that use the 88 gram bottles only.
This is a pack of 5 nose High Quality O rings and a small sachet of seal Lube for the 88 gram Co2 bottle.
It is wise to Check and or change these on a regular basis to ensure that you don't wast your bottle of 88 grams of Co2.  Otherwise you can watch the £7.00 pounds worth of gas escape.