The gearing industry has developed many unique measuring techniques for the production control of their products. Each technique has inherent advantages and limitations which should be considered by designers and manufacturers when selecting their use. Double flank composite inspection@ (DFCI) is one such technique that can functionally provide quality control results of test gears quickly and easily during manufacturing. The successful use of DFCI requires careful planning from product design@ through master gear design and gage control methods in order to achieve the desired result in an application. This document explains the practical considerations in the use of double flank testing for the manufacturing control of spur@ helical@ and crossed axis helical gearing including: oa general description of double flank inspection equipment including an explanation of what can be measured. orecommendations on practical master gear design. othe calculation of tight mesh center distance and test radius limits. othe resulting backlash that can be anticipated in gear meshes based on applying double flank tolerances in a design. oinitial and ongoing statistical techniques in double flank testing and how they can be practically used to improve gear quality. odouble flank gage measurement system analysis including case studies of gage repeatability and reproducibility (RR) and uncertainty analysis.