Vibram Siren is an innovative sole available only on Merrell shoes. The tread is composed of two levels. The first is a bottom layer of gray rubber that determines the foot's roll and features Vibram TC5+ rubber treads which feature differing profiles depending on where they are on the sole. The top black layer features a series of side strips that ensure uphill power and downhill precision, while the “little spikes” and the heel offer the stability necessary when making contact with the ground. Finished with a high-power shock-absorbing thermoformed Eva wedge, Merrell’s Vibram Siren is definitely ready for off-road sports.