Mattress Rock $77.00 Per Tonne Mattress Rock 50-100mm Great for Septic tanks, backfill and soakage Priced per Tonne TIP: IF YOU KNOW HOW MANY tonnes YOU REQUIRE, SIMPLY UPDATE THE QUANTITY FIELD BELOW AND ADD TO ORDER. Alternatively, use the following Calculator to guide you on the quantity requirements. The Calculator will advise the tonnes you need and you can add that total to your order. VIEW