Heavy Duty Tension Spring - High Strength Industrial Extension Springs for Garage Doors, Trampolines, and Heavy Machinery | Durable Metal Coil Springs for Home and Commercial Use

Fence springs are installed to allow extra stretch in the hi-tensile wire as well provide a visual cue for the amount of tension on a wire.  

When the spring is compressed to the first notch in the drawbars, it is under 150 pounds of tension, which is the recommended amount of tension. Do not over-tighten your electric fences!