The Redland Westminster Slate Clay 8.8k Thruvent is available for roof space ventilation, mechanical and soil pipe venting.Description Redland's Westminster Slate is a large format, single lap interlocking flat clay tile with variable gauge with a full range of complementary fittings and accessories.   Westminster Slate is a coste effective high-performance roof covering. With a tapered leading edge providing an exceptionally thin appearance and a hidden interlock, Westminster Slate is an elegant clay tile, engineered to perform at pitches as low as 17.5.    With a coverage of less than 10 tiles/m, it is simple and quick to install offering savings in both materials and labour. Available in 3 classic colour choices: (79) City Black, (80) Cardinal Red and (82) Old College Red.