This replacement head harness assembly is designed to be used with 3M™ Secure Click™ Half Facepiece Respirators HF-801SD, HF-802SD, HF-803SD (sold separately). Approved 3M™ replacement part designed for use with 3M™ Secure Click™ Half Facepiece Respirators HF-801SD, HF-802SD and HF-803SD (sold separately) Helps maintain regulatory performance requirements of respirator Easy installation allows for quick replacement Head harness assembly can extend service life of facepiece The 3M™ Secure Click™ Head Harness Assembly for HF-800 Series with Speaking Diaphragm, HF-800-04, works with 3M™ Secure Click Half Facepieces HF-801SD, HF-802SD, HF-803SD (sold separately). This harness is easy to install, can extend the service life of respiratory protection.