The Space Shuttle main engines (SSME) are the most advanced liquid-fueled rocket engine ever built. Featuring variable thrust, high performance, reusability, total redundancy, and a fully integrated controller, the performance of the SSME is the highest thrust for its weight of any engine yet developed.

The SSME's gimbal bearing is bolted to its main injector and dome assembly and is the thrust interface between the engine and orbiter.

This bolt and nut set were part of such an assembly flown aboard the orbiter Columbia (their last flight was STS-55 in 1993) and were disposed after they achieved "torque cycle limits." Engineers working for the Lockheed Space Operations Company deemed the bolts uneconomical to repair.

Interestingly, the accompanying paperwork identifies the value of each bolt at $550.00 per unit, with each nut worth $161.75.