Everlast 100-Pound C3 Foam Heavy Bag 100-pound professional-training punching bag with Contoured Closed Cell Foam Technology (C3) Polycanvas shell for durability Natural and synthetic fiber filling blended with sifted sand for a homogenous feel C3 designed to provide increased cushioning and force dispersion while maintaining bag integrity Durable webbing system with heavy-duty nylon straps and double end loops