The timber is ACQ (Alkaline Copper Quaternary) treated. ACQ is the preferred treatment for timber used in environmentally sensitive areas. It gives the timber long-term protection against rot, fungal decay, and insect attack. As well as durable timber, all the plastic parts of this swing set have been UV-Stabilised to resist fading and degrading in the harsh Aussie sun. All steel parts are double galvanised and powdercoated which will keep them rust-free inside and out, so that they'll last ages! The seats on this swing are easily height adjustable so both big kids and little kids can enjoy it! You know you're getting strong, durable timber with this top quality New Zealand Pine swing set.