The largest for your professional DSLR, battery handle, mounted lens and two to three other lenses.
Lowepro says it fits in:
DSLR camera with professional dimensions, battery handle and attached lens (e. g. Canon 5D Mark III with 70-200mm, f/2.8)
2-3 additional lenses
1 compact tripod, monopod, trekking poles
10" Tablet PC in the "CradleFit" device compartment
Designed for photographers who need a versatile backpack to protect their camera and outdoor equipment. The Flipside Trek is the perfect balance between camera compartment and free luggage space and comes with all the features you would expect from an outdoor backpack.
50% camera compartment, 50% free luggage space for personal items. The flipside opening allows the equipment to be removed without having to take off the backpack. The ActivZone harness system offers all-day comfort. Multiple mounting points allow increasing or decreasing the amount of equipment mounted on the outside. The integrated All Weather AW cover can be unfolded from a zippered compartment on the backpack lid to protect against rain, snow, dust and sand.
The padded CradleFit compartments provide support and protection for your Tablet PC. Stretch mesh pockets on both sides of the backpack hold water bottles and other items.…more