Portable, digital scale and conformity gauge keep you up to speed on your racerís weight and dimensions. Instantly check car weight to within .01 of an ounce. Measure overall width and length, width between wheels, track clearance and locate the carís center of gravity with the handy fulcrum point. Use the mathematical formulas and simple table to determine optimum placement for your carís center of gravity (CoG). Adjust for optimum speed and stability. Kit Contents: Digital Scale; Double-sided Reference Ruler; CoG Formulas; CoG Table for 5 oz Cars; and Two AAA Batteries. NOTE: Car kit with wheels shown in picture is an example of what can be built, but is not included.