Gravel & Toppings | Crushed Rock 20mm - Cubic Metre | All Green .20mm Crushed Rock is crushed granite. Also known as road base or blue stone · Economical · Ideal for use in base for driveways, pathways and nature.20 mm crusher rock,Gravel & Toppings | Crushed Rock 20mm - Bagged | All Green .Crushed Rock 20mm - Bagged. Code:133025. Description: * Ideal base for driveways, toppings and concrete. * For best results use a wacker plate for compaction. * Approx Bag Size = 20kg * Approx 1 cubic metre = 75 bags.