These hand crafted planters are made using the highest quality oak. not given The internal walls are painted with a thick rubberised paint sealant creating a barrier between the timber and the soil which will need to be reapplied after 5 years to prolong their life. If left untreated and outdoors, the oak will silver over time. The slatted base is made from a timber called Balau which is highly durable. You will need to place a permeable membrane in the base of the planter to prevent soil falling through. oak