The Petzl Bug is designed specifically for single day,  multi-pitch rock routes. The rounded rectangular shape maximizes volume and minimizes interference while in use. There's enough volume for carrying approach gear without getting in the way when climbing. Everything has been designed for maximum comfort while climbing: minimal bulk, mesh and ventilated foam shoulder straps allowing freedom of arm movement, ventilated back panel, tuckaway waistbelt, high positioning away from your  harness and lateral compression straps to keep everything tight.