Why the HP PROTECTUS® III (S)? The HP PROTECTUS® III S (Stainless Steel) fire service meter measures extremely wide flow ranges at 100% ± 1.5% accuracy. All HP PROTECTUS III S meters meet or exceed AWWA C703 Standard, are NSF/ANSI 61 Certified, and Underwriters Laboratory (UL) Listed and Factory Mutual (FM) Approved for fire service use.