A flow that typically begins with very few raw materials that proceed through production resulting in very few finished products.

“I” plants are typically dedicated lines. Typically the line produces only a limited number of products, and it works on only one product at a time (flow lines).

Examples: Food and Chemical industries, Sheet-metal fabrication, etc.

OR
The production flow has a sequence of several operations repeating itself – the product goes through the same set of operations several times.

Source: Oded Cohen and Jelena Fedurko, Theory of Constraints Fundamentals, 2012