Paint & Wall Coverings
Spear and Jackson 2 x 5L Black Spot Remover and Destroyer - Ready to Use for Natural stone, Concrete, Paving slabs, Indian Sandstone & Limestone
Remove black spot from block paving, concrete or natural stone 5 litres of product will clean and treat approximately 25 m² Helps to lift and clean dirt and grime from areas that haven't been treated for years - you'll have them looking brand new...
https://www.bizrate.co.uk/paint_wallpapersupplies/spear-and-jackson-2-x-oid13447694070.html