The picnic backback is a key item within our extensive Insulated Lunch Bag selection.To choose the right size insulated lunch bag for school, measure the lunch box or containers you pack most often and pick a bag slightly larger so there’s space for an ice pack and snacks. For younger kids, a bag about 8–10 inches long usually fits a sandwich, drink, and snack. Older children often need a 10–12 inch bag to hold larger containers, drinks, and an ice pack while still fitting easily in a backpack.