The Grower's Edge? EZ Lock-n-Release Plant Support Spool is a state of the art trellis hook that enables you to easily, rapidly and safely lower and train your plants. The specialized lock also prevents the unit from accidentally coming off the supporting overhead wire. This trellis spool is composed of a metal hook and pre-wound spool with 105 feet of UV resistant twine to last up to back-to-back crops before needing replacement. Works great with Grower's Edge? Crop Clip and Vine Clips.