The Titan Pro Knee Guards provide D3O® armor protection, while the Posi-Lock buckle system features one-time strap adjustment and quick-release functionality. Range of motion is assured, care of the hinging system which allows the knee cap to move independently while riding. Variable Axis Hinge allows knee cap to flow up and down independently, for increased range of motion. Posi-Lock buckle system allows quick release after strap adjustment has been made. Fully-vented knee and shin with nested D3O® Armor dampening. Compression-molded liner for superior comfort. Sold as a pair. D3O is a long-chain polymer with off-shoots. The intelligent molecules move freely among themselves and, in the case of a collision, they move past the off-shoots together and spread the force over a large area. The D3O protectors are very soft, flexible and thin. And, they adapt to fit the body.