The MSR SweetWater Purifier Solution in for use in conjuncture with the SweetWater Microfilter. The combination of these purification vessels is crucial in eliminating 99.99 percent of waterborne bacteria, viruses, and common protozoan parasites that your water filter alone can’t get. And it’s easy to use, just filter a liter of water with the SweetWater Microfilter, then add five drops of SweetWater Purifier Solution. Mix for 10 seconds and wait five minutes for the solution to do the trick. And just for a heads up, this solution has only been approved for use with the SweetWater Microfilter.