Used mainly with drive screw nails and spring head roofing nails for attaching corrugated roofing sheets to wooden purlins. The washer provides a watertight seal when used correctly. To Fit Screw Dia. mm - 8.0To Fit Screw Gauge imp. - N/AOuter Dia. mm - N/AColour - BlackMaterial - PlasticFinish - Matt Timco Dowty Type Washers (Size M8 x 30mm - 75 Pieces) in Black Size: 1000mm x 1000mm