SummaryThis predator guard goes on the outside of your bluebird nest box and reduces the risk of predation. Included is the openscad file, so you can modify any of the parameters for this guard to suit your needs. Including depth of the tunnel, width, and height. The parameters are set for an elliptical opening generally agreed to be optimal for eastern bluebirds. You are free to modify it for other species or your local. Chears and safe birdingInstructionsPrinted with zero extra shells and 100% fill for strength. PLA might be preferable to abs.