Air­line reg­u­la­tions have resulted in many annoy­ing restric­tions for folks who want to bring a lit­tle bit of every­thing along on their trav­els. Aside from other neat fea­tures, this design solves a key prob­lem for such fre­quent fly­ers: you can keep up to six liq­uids in a sin­gle con­tainer, rather than hav­ing small bot­tles roll around sep­a­rately inside a lit­tle plas­tic bag in order to fit fill limits