The Thermacell refill pack R-4 is a 48-hour refill pack consisting of 4 butane gas cartridges and 12 active ingredient plates. All Thermacell units use the same refill products. A gas cartridge lasts up to 12 hours, an active ingredient plate up to 4 hours. Gas cartridges and active ingredient plates can be stored and do not have to be used up immediately. Unused active ingredient pads are packed airtight to maximise shelf life.