The front piece can be unscrewed and removed depending on which species of bird you wish to attract. It also allows for easy cleaning. If you decide to use the hole-front then this nest box is suitable for: Blue Tits, Coal Tits, Great Tits, House Sparrows, Tree Sparrows and Nuthatches. Alternatively, the open-front will attract Robins, Wrens and Blackbirds.Dimensions H 210mm x W 120mm x D175mm