All our square timber is pressure treated, unless specified otherwise, using the new generation Osmore Celcure Ac-500. This process is when the timber has been impregnated with Osmose Celcure Ac-500 wood preservative designed to protect the product against wood decay and insect attac. Osmose Celcure Ac-500 treated timber can be used in a multitude of ways from agricultural fencing, garden projects and construction.