Description Blue Gravel Screenings 20mm is perfect for use as a drainage medium or for garden paths and driveways. Blue Gravel is available in 4 sizes – 5mm, 10mm, 14mm and 20mm and also available in 20kg bags. Features of Blue Gravel: As a drainage medium Used as a garden path or for driveways Available in 4 sizes 5mm, 10mm, 14mm & 20mm Also available in 20kg bags Gravel Delivery: Pebbles and gravels are sold by the tonne, and are available online or in-store. Delivery across Adelaide starting from just $39.