A real scale chain-link chain for for trucks, tow trucks, '50's and earlier pickup tailgates, dioramas, even snow chains (if you have the patience).
This is available in 4" increments for any length you want, with a minimum of 4".
Made of stainless steel and linked together like a real chain.
Here's an example of how Bob Barranger used it for a rear end safety system.
Stainless steel chain cut to length, 1/25 scale, by Ted's Modeling.