Roofing Industry Standard. Select from M8 x 60mm - M8 x 300mm. Select from M6 x 60mm - M6 x 160mm. Hook Bolts, Square Nuts, Roofing/Spat Washers & Top hats. Black Nylon Top Hats & Roofing/Spat Washers - Provides a watertight seal when used correctly.
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