ah! i had forgotten what the blades were for.. now i remember.. thanks.
strangely, many of my colleagues' rides do not have a tire inflator.. they find mine cute, kinda what they used when they were riding bicycles in their childhood.. the foot-operated ones get easily destroyed. the cigarette lighter plug-ins were pretty much one or two use only. the nice ones cost upwards of 2K, but they work faster, and they last longer.. but the manual foot-and-arm models actually last long, not to mention the exercise, 'cause you really have to be athletic to inflate a tire from zero...