The SteriPEN Classic with Pre-Filter Pack is perfect for those who already own a wide-mouth water bottle. Like the Safe Water System Pack (but without the bottle), the Classic with Pre-Filter pack is all that is needed when camping, hiking, backpacking or traveling. Use the 40x40 micron screen Pre-Filter to remove particulates from the water. The Pre-Filter is designed to be stored directly on the wide mouth bottle. Includes a neoprene carry case and User Guide.