Nest boxes with plastic insert from the company OESIEG : • Size: 25 x 21 x 25cm (H x W X D) • with plastic insert The wooden concave can be replaced by a cardboard insert after all the young birds have hatched. When the nest box is cleaned regularly, the cardboard insert is thrown away and replaced with a new one. This ensures that the nest box is always clean, but can still be cleaned easily and efficiently.