Precision Clean Breather Bags® are designed for sterilization of products used in cleanroom & critical environments. Precision Clean Breather Bags have excellent porosity for enhanced cycle times and are manufactured with the strongest Tyvek®-bonded seals available. Precision Clean Breather Bags are manufactured from ultra-pure and clean resins with one side of 1059B Tyvek and one side of .003? Precision Clean® High Density Polyethylene film in our ISO Class 4 cleanroom.