Embodiments of the present invention include bicycle chain rings for bicycles having specially shaped ramps, tapers and profiled teeth for improved shifting performance. Accordingly, when the movable core contacts the stationary core, the buffer can be pressed and transformed to decrease impact and noise. At one end, the pouch includes a releasable clip adapted to secure the pouch to an article of clothing worn by the individual in a position where the pouch is concealed. Spacer elements in such pump chambers are, in some embodiments, attached to a wall of the substantially rigid component so as to prevent the movableflexible membrane from contacting the wall during pumping.