Piston rods are long, straight metal bars that connect the piston to the crankshaft in an engine. They help convert the up-and-down motion of the piston into the rotational motion of the crankshaft, which powers the engine. Full definition
The dampers have new piston rods to reduce friction for more efficient control which translates into a feeling of greater body control with better bump absorption. (ferrariofseattle.com)
It's also true that they separate on the shelf if stored vertically, piston rod up or down. (mechanics.stackexchange.com)
Obviously though if the shocks have damaged piston rods, valves or they've been leaking gas / fluid then they'll need replacing. (mechanics.stackexchange.com)