Fizik Tundra M5 Mountain Saddle. Driving a M5 in an Arctic wasteland may not make much sense, but what's a marvelous idea is slapping the Fizik Tundra M5 Mountain Saddle on your cross country rig. The robust and abrasion resistant Microtex cover can handle whatever punishment you dish out while at 220 grams it won't weigh you down on the climbs. As part of Fizik's Spine Concept fit system, the Tundra M5 is optimized for those who have a high level of flexibility in their spine if you can reach down and touch your toes while standing you're a Snake in Fizik fit parlance and as a result the saddle's shape is flat, narrow and long. Additionally, the Wing Flex shell flexes downward where the inner thigh contacts the saddle, allowing more efficient pedaling and full range of motion.