Scoring An Impressive 88% On The Which?test For Bird Boxes.woodcrete Nest Box Is made From An Ingenious Mix Of Sawdust, Concrete & Clay. Guaranteed For 25 Years!weatherproof & Rot Proof The Woodcrete Nest Box Offers Excellent Insulation & Durability Against All That The British Weather Can Throw At It. removable Front Panel For Easy Access & Cleaning. 32mm Hole, Ideal For Most Small Common Birds – Great, Blue, Marsh, Coal & Crested Tits, Redstart, Nuthatch, Flycatcher, Sparrow, Wryneck & Bats!