For fast adventures in the mountains up to 2 days, the light, durable Synapse Flow 45 has dynamic shoulder straps that make it easier to move, as well as an airvent system for ventilation and an integrated rain cover. Motion U Frame. Airvent Flow. Motion Fit Hike. Dynamic Shoulder Straps. Airmesh Belt. Adjustable Sternum Strap. Compression Straps. Load Lifter Straps.