This product is known as shock cord or bungee cord. It will stretch to 100% of its original length. Comes in white with black tracers or all black.
5/32 Bungee Shock Cord - Black – Atwood Rope MFG
SGT KNOTS Shock Cord (1/8 inch) Diamond Grip - Black Elastic
T.W. Evans Cordage 3/8 in. x 100 ft. Elastic Bungee Shock Cord SC-308-100 - The Home Depot
Mytee+Products+50+Pack+21%22+EPDM+Rubber+Tarp+Bungee+Straps+with+Crimped+Hooks+ for sale online
T.W. Evans Cordage 1/2 in. x 100 ft. Elastic Bungee Shock Cord 72120 - The Home Depot
Marine Masters 1/8 inch X 100' Blue Bungee Cord - Polyester Marine
NeoStretch 1/4 Slip-Resistant Textured Shock (Bungee) Cord
3/8&&-9mm Black Polyester Shock Cord 100 ft
T.W. Evans Cordage 3/16 in. x 500 ft. Black Elastic Bungee Shock Cord SC-316-500 - The Home Depot