Hard Hat Suspension, Head Protection Suspension Type Ratchet (4-Point), Fits Hat Size One Size Fits Most, For Use With Vanguard(TM), Compatible Hard Hat/Helmet Brand Name MSA SAFETY, Compatible Hard Hat/Helmet Grainger Part Number 3PB96, 3PB97, 4RB42, 4RB43, 4RB44, Compatible Hard Hat/Helmet Manufacturer Part Number 804939, 804940, 804944, 804946, 804947