Good luck sourceing spare burst disks....if anyone has some I have a few people who will buy immediately....even the makers WDP have no stocks. As already said the air fill adapter is different and if the old one is still in place an adapter will be needed..Planet did have them. Also a great many had the filter removed from behind the fill nipple as they are ok to use but really do restrict the flow into the bottle when filling. To follow on from the beginning of my post if your burdt disk is missing......may well be and will have been replaced with a cut coke can...DO NOT USE or even attempt to do this so called "fix" when you do blow your burst disk. The burst disk is crimped to the nut so you should not have any kind of loose disk installed.