Hayward® HCF342C 42" HCF Series Commercial Bobbin Wound Fiberglass Sand Filter. The 42" HCF Series Commercial Bobbin Wound FG Sand Filter is designed to provide the ultimate in filtration performance and durability. Its larger size eliminates the need for multiple smaller filters, which means you’ll save valuable floor space, reduce installation and plumbing complexity, and simplify maintenance and backwashing. Constructed with heavy-duty filament-wound fiberglass and UV-protected resin, as well as corrosion-proof internals, this large-format HCF Series sand filter offers a powerful, streamlined filtration solution.