with tunnel and ladder for hanging opening in base plate for easy cleaning bark wood We attach the highest value to your pet's health. For this reason, our Natural Living items are made of coniferous wood without resin canals, as resin can be poisonous for some animals. The types of wood we use do not exude resin and are dried extensively before being processed as well. The glue we use is also non-toxic for animals and consists of a rubber or cellulose mix.