Simple stock: This simple stock represents the amount of stuff that we are measuring over a period of time. The units of this stock is pounds.

Flow in: This flow represents some amount of stuff going into the stock "Simple Stock". The units are pounds per day.

Flow out: This flow represents some amount of stuff going out of the stock "Simple Stock". The units are pounds per day.

Converter A: This converter changes the amount of stuff going into "Flow In".

Converter B: This converter changes the amount of stuff going into "Flow out".