What improvement in manufacturing did Eli Whitney popularize

Eli Whitney popularized the interchangeable parts.

Explanation:

Eli Whitney invented the interchangeable parts theory. This technique affected the design part of a product, by dividing it into elements that would be designed separately by maintaining a series of relationships with each other that allowed them to be assembled in order to obtain the final product. Whitney put it into practice for the manufacture of muskets for the United States military, drawing on similar work that had been done long ago by the French inventor Honore Blanc for the French army. This was the basis of parts production and spare parts.