These look like the shocks that are used on monster trucks to dampen the hard landings. IF they are of like design, then the small reservoir is nitrogen filled and the shock itself is filled with oil. The oil spills into the gas reservoir under load and presses a gas piston to compress (and thus dampen) the shock. This type of shock was specifically developed for monster trucks when it was found that normal shocks were just too bouncy. Unless you make high jumps with your bike (I doubt you do) these are way overkill for the normally ridden cruiser. My source for this info was a segment on Monster Trucks (duh!) on Modern Marvels (History Channel).
