a front inner tube, which works in the rear as a temporary measure, the last time I had a puncture, I was in France and the bike shop I got taken to had no spares, plenty or tyres in 16" or 172 but nothing in 18" and not a single tube ,the bloke removing and refitting the tube, might not have even seen an inner tube before, from what I gleened whilst watching, and aiding him! he was trying to use bucycle tyre technolodgy of 20 years distant (maybe)
without that tube, I might have waited 48 hours or more.
CLEM