Replacement Lead Line Freedom Aerial Dog Run Polypropylene 15 Ft Dog Tether Manufacturer suggested replacement lead line for Freedom Aerial Dog Runs. Heavyweight Polypropylene Better than Nylon in and Around Water! Excellent UV protection, low stretch, and does not absorb water quickly giving it a better resistance to mildew and rot. Also can be used as a dog tether. Made in the USA and has one year warranty.