YKK North and Central America Group manufactures airtight and watertight zippers used in OSHA Level A and NFPA 1991 & 1994 suits for full liquid chemical and chemical vapor protection. Our water resistant zippers are used in OSHA Level B and NFPA 1992 suits for splash protection. When designing Personal Protection Equiptment, select a proven YKK® PROSEAL®, AQUASEAL®, or AQUAGUARD® zipper.