The Airport Essentials is the smallest ThinkTank Airport backpack, designed around a standard depth SLR body. If you don't have a deep-body pro SLR, the Essentials' 5mm reduction in depth reduces the bulk of a backpack quite a lot, but it will still hold a 300/f2.8 with body attached, or 4-6 lenses plus accessories. It also holds a 13" laptop and an iPad in separate compartments. The harness has lumbar support and mesh panelling to help keep your back cool, and includes a waistbelt.