For Use With Natural Slate & Man-Made Slate. FILON has been producing GRP (Glass Reinforced Polyester) products for over 50 years and produced the first GRP valley gutters for the UK market in the 1980’s. The V-Flow DF valley trough range caters for tiles and slate roof materials and allows for even the deepest tile profile to be used, with the GDFVT110 valley trough. This dry-fix system has been developed to eliminate the problems associated with the use of cement mortar and is finished in grey to simulate the appearance of lead. Features The flexible closures are finished in matt black. Filon V-Flow DF valley troughs have a minimum life expectancy of 20 years. FILON’s V-Flow DF valley troughs and accessories are fully recyclable at end of life. Note Comes with set of packing pieces.