Hang on Sheperds Hooks or poles up to 1 inch in diamater Models for single or multi-hook Shepherds Hooks. Keeps squirrels on the ground and your bird feeder Squirrel Proof. Length expands up to 48 inches. The Squirrel Proof II Spring Device is compatible with multi-hook poles. It wraps around it instead of slipping over the top. It secures in the same fashion as the Squirrel Proof I Spring Device.