NOTE: Due to a component change in the Jetboil Personal or Group Cooking Systems’ (PCS/GCS) valve assembly, the small spindle O-ring replacement in the PCS/GCS maintenance kit may not be appropriate for all PCS/ GCS. If you have purchased or will purchase a PCS maintenance kit, do not use the small O-ring to update your PCS or GCS. If you suspect that the spindle O-ring inside your valve needs replacing, please contact Jetboil Customer Service at 888-611-9905. The spindle O-ring is the smaller of the two O-rings in the Jetboil maintenance kit, SKU MNT100.