#4 rebar: 0.500 in diameter, 0.668 lb/ft, 0.20 in² cross-section area. ASTM A615 Grade 60 (60 ksi yield, 90 ksi tensile). Deformation pattern per ASTM A615 for bond. Sizes: #3 (3/8 in) through #18 (2-1/4 in). Common uses for #4: slab-on-grade (per ACI 318), foundation walls, retaining walls, residential footings, masonry grout cells. Lap splice length: 30-48 bar diameters depending on conditions (typically 24-30 in for #4). Cover: 3 in earth contact, 1.5 in exposed to weather, 3/4 in interior. Corrosion protection: epoxy-coated (ASTM A775), galvanized (ASTM A767), or stainless steel for marine environments. Cost: $0.40-$0.80/ft ($800-$1,200/ton). CSI 03 21 00. Placing tolerance: ±3/8 in for cover, ±2 in for spacing.