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Small Path

Small Slabs

Garden edging

Our One Mix Post Mix is a perfectly proportioned blend of cement, aggregate and sand especially designed for setting fence posts, logs and letterboxes into the ground. We have created this formula to develop a sturdy yet pliable consistency that can be applied to the area whilst stabilising the pole or log throughout the curing process. This ensures that your work remains level and balanced whilst the product dries and hardens.

Why you need this product:

  • Optimal consistency for the installation of posts and logs
  • Maintains position whilst setting to reduce the need for excessive structural support
  • Economical alternative to using concrete
  • Compressive strength of 15MPa – 20MPa when fully cured

* MPa is the metric unit for pressure or stress called megapascal (MPa). The term is used in concrete as the common unit for compressive strength.

How to install a letterbox using OneMix Post Mix

OneMix presents an easy, step-by-step guide on how to use OneMix Post Mix when installing a letterbox.


Post Hole Dimensions


Post Type


Results (Approximate)

Volume of concrete =
No. Bags Required
Volume of Water per bag