Bilateral Support Hinges for stability and increased performance. Patent Pending X-Fit Strap System. Bilateral Support Hinges with Hyperextension Stops and Impact Absorbing Base Pads. Tempered Aluminium Stability Stays securely anchored within Hypalon sleeves. Anatomical Precurved Design. Four-Way Stretch Lycra Mesh at back of knee. Premium Stitching Assembly, Patella Support Finishing and Lycra Binding for long lasting comfort. Convenient Finger Tabs offer easy grip pull when fitting. N-Tex Vented Neoprene. Measure knee circumference 2" = 5cm below center of kneecap (patella) Size Large Knee Inches 13.75–14.5, Knee CM 34.9–37.5