You will always be dry when sitting outside on these blankets. The underside is made from waterproof nylon fabric. Large Tweedmill Picnic Blanket The area of 137 x 183 cm (54” x 72” approx.) gives enough space for at least two people & the picnic. 100% wool in " Hunting Mc Leod" tartan. Underside made from strong green 4 oz nylon, waterproof to 6, 000 mm water column, two carrying handles, two large compartments.