Much like Jekyll and Hyde, the CamelBak Blowfish Hydration Pack changes size and shape for no apparent reason. Well, actually the reasoning is quite sound: you can match your pack to the task at hand. Although it won't have you murdering random people in the streets of London or testing new grounds of chemistry, the Blowfish will have you pedaling like a monster, a hydrated monster that is. Zip it down for short rides or hikes, or let it expand if you need to bring along a jacket or a big lunch. Once lunch is over, you can zip it down from 1100 to 670 cubic inches of space so you don't have unwanted backpack material flopping around. An Air Channel back panel and Air Mesh harness allow air to circulate through your shoulders and back, preventing moisture built up and discomfort. Pack your bike tools, music, and phone in the bike tool organizer and media pocket respectively while the nylon, diamond Clarus, and polyester protect your stuff with a water blocking DWR and PU treatment. Both the front and back sport reflective panels, as well as a blinker tab, for extra safety when cruising nocturnal streets. Though not quite the potion Dr. Jekyll was seeking, this two liter Antidote reservoir will cure your thirst for about two hours on the ride. At the turn of a cap a quarter turn to be exact, you can open or close the reservoir, refilling and securing it again in seconds. Center baffling and a sleek design prevent your water from jostling about inside your pack while running, hiking, or hitting the park. Since last year, CamelBak's go to reservoir system has actually lost some weight, reducing bulk in the fill port and offering you that much more convenience.