Hunter's Specialties Spring Yelp'R Box Call is a unique box. Besides its construction of American poplar and walnut it is a one-sided call with a unique spring design. The spring is a compression/torsion spring. It not only controls the tuning by way of screw depth but also allows the user one-handed foolproof operation. Help open in place one only must stroke tap or slide to get all kinds of vocalizations from yelps cutts clucks whines and purrs. Automatically returning to home base each time.One sided call with spring design allows one handed operationBox made from American Popular with Walnut paddleCompact designWeight: Approximately: .37 poundsShipping Dimensions: Approximately 12 x 4.5 x 2.5 inches