3M™ Head Harness FF-400-04 is a single head harness replacement for use with the 3M™ Ultimate FX Full Facepiece Reusable Respirators FF-401, 402 and 403. 3M™ Ultimate FX Full Facepiece Reusable Respirator FF-400 Series are reusable respirators that offer comfort, durability and ease of cleaning. It features a soft feel to the face, comfortable head cradle, plus reduced heat and moisture buildup, 3M™’s Ultimate FX Full Facepiece Respirator delivers a comfort that lasts as long as you do. And it’s the only respirator with 3M™’s Scotchgard™ Paint and Stain Protector, which helps keep the lens dirt-, paint- and stain-resistant — not to mention so much easier to clean.