Sold by the foot, Cut to your desired Length: 
This is the same ¼" cord we use with the Hulk Handles.
I prefer 3' to 4' lengths with a loop tied at each end.
 
HIGH ELASTICITY FOR REPEATED USE: Designed with high quality rubber, enabling them to stretch significantly and return to their original shape after use, which makes them durable and reliable for repeated applications without losing their effectiveness  
WATERPROOF: Neither the rubber core nor the sheath will be damaged by water. As such, they retain functionality whilst wet and are suitable for prolonged outdoor use