The Ruffwear Singletrak Pack is a sleek, low-profile hydration pack. Featuring two on-board, collapsible water bottles, dogs stay hydrated for the long haul. Two external stash pockets fit other adventure essentials. The Singletrack Pack is available in 3 sizes. Select the correct size based on your dog's girth (measurement around the widest part of the rib cage). Inbetween sizes: choose the smallest size. Small: 22-27 inches (56-69 cm); Medium: 27-32 inches (69-81 cm); Large/X-Large: 32-42 inches (81-107 cm). Weight & Capacity: Small: 0.7 lb (0.32 kg) / 195 in³ (3.2 L) capacity; Medium: 0.91 lb (0.41 kg) / 195 in³ (3.2 L) capacity; Large/X-Large: 1.05 lb (0.48 kg) / 195 in³ (3.2 L) capacity. Washing Instructions: Pack: Secure the fasteners; Remove collapsible water bottles; Hand wash with mild detergent; Hang dry. Bottles: Hand wash with dish soap; Rinse thoroughly; Air Dry; Store with cap removed.