Grocery sizes. In fact, a lot of them already have it on the items. Typically because a lot of products are also sold in Canada so they put the ml measurement next to the gallons.

> manufacturing

This is sadly far from the truth. Manufacturing is nowhere near metric conversion. Horsepower, foot-pounds, and my all time least favorite unit, the mil, are everywhere. And relatedly, manufacturing execution systems that use localtime internally cause all manner of hilarity twice a year. It’s like we’re just deliberately trying to be bad at measuring things.