Hubless cast iron: ASTM A888, CISPI 301. Joined with no-hub couplings (neoprene gasket + stainless steel clamps). Sizes: 1-1/2 in through 15 in. Wall thickness varies by service weight. Weight: 4 in = 4.8 lb/ft. Fire resistance: noncombustible, 2-hr fire rating through assemblies without additional protection. Sound: STC 46+ (vs PVC STC 36). Required in many commercial specifications. Cost: $8-$25/ft for 4 in (2-3x PVC). Lifespan: 75-100 years. Advantages: fire resistant, quiet, durable, code-required in many Type I/II buildings. Disadvantages: heavy, more expensive, requires pipe supports at closer intervals. CSI 22 13 13. Fittings per ASTM A888. Support spacing: 5 ft horizontal, every story vertical.