The new Maxima RED® SD is a breakthrough in controlling Dynamic Spine in a smaller diameter (.203"ID) shaft. The new, high-tech carbon arrow shaft design has stiffer ends to contain the arrow's flex to what we call the RED ZONE®. The RED ZONE is the section of the arrow shaft engineered to contain Dynamic Spine and make a broadhead shoot more consistently. The smaller diameter Maxima RED® SD delivers improved penetration and reduces wind-drift which enables more accurate shots at longer distances. - Matched Set: All Maxima RED® SD 6- and 12-pack sets are sorted and matched by weight and spine for best-in-class consistency. Spine selection sorting tolerance is +/- 0.0025". Weight sorting tolerance is +/- 1.0 grains. - Real Straightness: Every Maxima RED® SD arrow is laser checked for straightness to a remarkable 1/10,000 of an inch. Maxima RED SD straightness of +/- 0.0025" is a maximum measurement, not an average.