I use a cheapo China make bag called the Backpacker BBK4, which big enough for all my stuff, which include either my 7D+ 70-200mm f4L, Tokina 12-24mm and Sigma 17-70mm lens, monopod (or small tripod), remote control, external flash (YN565EX), my set of filters (ND, Polariser, etc), two 1 litre water bottle, lots of plastic bags, umbrella and some Uncle Toby energy bars or my OMD with 3 to 4 lenses, monopod (or small tripod), remote control, external flash, my set of filters (ND, Polariser, etc), two 1 litre water bottle, lots of plastic bags, umbrella. Other than that, the bag can be used to put my 14inch computer, jacket, Microsoft Surface RT, Asus Nexus 7 and some notes for my school work.