Depending on the volume of items you need to stash away, choose accordingly. Storage is measured in gallons. Watch out for exterior dimensions to get an idea of the overall size of the bench. Outdoor storage bench comes in 3 sizes:  small, medium, large and extra-large. For up to 50 gallons, small boxes are more than enough for keeping a few cushions and hose pipe. Up to 70 gallons is good for small tools storage and gardening items like trowels. Extra-large benches have more than 150 tonnes storage and can be used for keeping blankets, pool accessories and bigger cushions. These occupy more space so should be selected accordingly.