- 4-1/8" Arctic White Polypropylene Cover Plate (39621) by Seachoice®. UV stabilizedAcetone resistant polypropylene Requires #8 fasteners. This top-grade product is expertly made in compliance with stringent industry standards to offer a fusion of a well-balanced design and high level of craftsmanship. Manufactured from industry-leading materials using up-to-date equipment, it ensures everlasting reliability and enduring value. This product is distinguished by total quality assurance, unsurpassed by anybody else.