An improved spray delivery system and method for aerosol containers is provided. The method further includes determining if the control signal is a fixed code signal or a rolling code signal. The bike rack includes a hub assembly, hitch insert assembly, and support wing assembly. The cover may be positioned over the cavity, and may also be positioned over part of the upper surface of the rigid component. The invention is particularly useful for determining the concentration of glucose in blood and is described herein with reference to that use but it should be understood that the invention is applicable to other analytic determinations.