Description of Thermarest Prolite 4 Regular Stuff Sack These superlight Stuff Sacks provide durable, water-resistant protection for your Therm-a-Rest Fast & Light mattress in the field. They include a handy clip loop and end handle for easy unpacking and portability, and are made of 30-denier silicone-impregnated nylon. Features: Fits ProLite 4 & Z-Lite Regular, folded in half. Weight: 0.8 oz. (23 g) Dimensions: 6.25 x 13.5 in. (16 x 34 cm.)