Abstract: A hollow plastic ball bat has an internally mounted swing metering device that provides a visual indication of swing velocity. The bat is defined by inner and outer members that are coupled to one another to define a recess that receives a transparent annular barrel. A bore in this barrel has a weighted piston that moves in the bore, as a result of its inertia, During a swinging or other movement of the bat itself.

Abstract: A device and a process for measuring fuel quality and/or economy is provided by this invention. The specific gravity of fuel is measured by any suitable means such as a hydrometer; the temperature of fuel is measured by another means, such as, a thermometer. Third means responsive to the measurements obtained by first two means converts the specific density of the fuel to specific density at a predetermined temperature and from that to fuel quality. The fuel quality can then be converted to fuel economy when the price of fuel is known. Alternatively, specific density of fuel corrected to the specific density at a predetermined temperature can be converted directly to fuel economy if the price of the fuel is known. For conversions described above suitable nomographs can be used.