S1 Replacement FilterSawyer S1 Select Filter SP4121 Foam Replacement All Sawyer Select systems reduce chemicals down to 0. 5 parts per billion (up to 40 times lower than the EPAs maximum recommended level) and reduce pesticides down to 0. 01 parts per billion (400 times lower than the EPAs maximum) Enjoy safe, clean water anywhere in the world with Sawyer Select Water Filters and Purifiers which remove virtually all contaminants found in fresh water while also improving