ISO 2768 is a technical standard for general tolerances in mechanical engineering (for linear and angular dimensions without individual tolerance indications).

Marco had spent twenty years designing precision gears for racing engines. Every night he came home, washed the coolant smell from his hands, and measured his life against the ISO 2768 standard hanging on his workshop wall: General tolerances for linear and angular dimensions.

He never exceeded those invisible boundaries. Until Elena left.

She didn't slam the door. She simply said: "Your heart has no tolerance class, Marco. It’s either perfect fit or rejection."

One midnight, he opened the old workshop. Among calipers and micrometers, he found a brass gear he’d made as an apprentice. It didn't fit any shaft. Its teeth were irregular. Scrap , his master had said.