Check the listing for details. 1" Predator Guard Wrens Birdhouse Brown. Color: Brown, Condition: New. Listed at 4.25 USD. Birdhouse Predator Guard 1" suitable for Wrens Size: 1" hole diameter (suitable for Wrens) Color: Brown The 2" Square Base Guards are available in sizes: 1-1/2", 1-3/8", 1-1/4", 1-1/8", and 1" diameters... NOTE: This item is 3D Printed using fusible thermoplastic (polymer) filament. A common bolt hole pattern has been designed into the 2" Square Series to allow different entry hole diameters to be swapped out within minutes without having to drill new mounting holes. This feature allows nesting boxes to be quickly adapted to the intended bird species preferred entry hole diameter... Both internal and external surfaces of the extended tube have a textured finish to allow native cavity nesting birds to easily grip the entrance surface... The predator guard serves to prevent chewing/gnawing predators from enlarging the entrance hole to gain access to the nesting cavity... it also assures proper sized entrance hole diameter... The extended entrance tube provides added distance between the predator(s) and the nest box inhabitants (eggs/young/parents)... The absence of a perch discourages predatory birds such as sparrows / starlings from easily perching themselves at the entrance of the nest box. Tube length (depth) approximately 1-1/4" Four 3/4" wood screws are included... This is an original design... often imitated, never duplicated... Designed by a birder to be shared with fellow birders and our feathered friends... *** INSIST ON THE ORIGINAL ***