TrailMax Horse Highline Tree Saver Straps (Pair) Prevents tree girdling when using horses on a highline Constructed of heavy 2" webbing and steel rings Sold in pairs. They prevent your highline rope from cutting into and damaging tree bark. These are highly recommended by the Leave No Trace backcountry ethics cooperative effort of the US Forest Service, the US Department of Interior, the National Park Service and the US Fish and Wildlife Service.