A. 7 " measured from knee center to bottom of plastic. Fits sizes 3'3 " to 4'1 ".
B. 8 " measured from knee center to bottom of plastic. Fits sizes 3'7 " to 4'4 ".
C. 9 " measured from knee center to bottom of plastic. Fits sizes 3'9 " to 4'7 ".
D. 10" measured from knee center to bottom of plastic. Fits sizes 4'3" to 4"10".

Contoured to fit, not made too wide as most others are. Multi-segmented hinged design makes for a close, anatomically correct fit. The two-strap Velcro system is designed for a no-slip fit for a more powerful, unhindered stride. Comfort foam knee donut and dual density foam delivers a snug, secure fit.