Just as a thought (coz it happened to me): I Used to use cartridges, and a few times on my daily commute I've only had 1 cartridge and 3 days til pay day and I prayed the whole time nothing would happen. If someone had needed my last cartridge - yuppers, they'dve had it. My thought is: that could be me someday and I hope someone out there comes along and helps me. I now have a Road Morph and have stopped several times and loaned them my pump and told them to save their cartridges in case someone isn't around the next time.