Hayward® HCF236C 36" HCF Series Commercial Fiberglass Sand Filter with 2.5" Bulkhead. The Hayward 36" HCF Series Commercial FG Sand Filter with 2.5" Bulkhead sets a new standard for performance and longevity in the recreational water market. Designed to improve filtration and lengthen filter cycles, it's made with a UV-protected gel coat that shields the filter against the elements, preventing fiberglass blooming. Its secure lid mechanism enables easy inspection, and with material like proprietary resins and fiberglass, it's also virtually corrosion-proof.