Hands down, the Dragons are Sidi's most advanced off-road shoes. The comfy Lorica uppers are durable, water resistant, and tougher than leather. The carbon soles offer amazing pedal power, comfort and durability. Plus, with Sidi's Caliper and Techno II buckles, Arch Compression Straps, High Security Velcro and adjustable Heel Security System you can dial-in the ultimate fit. Sidi designed the Dragon 2s to last, too. SRS stands for Sole Replacement System, which means you can simply replace worn soles and keep going.