What size do I need to pass TSA's 3-1-1 rule?

TSA caps individual liquid containers at 3.4 oz (100 ml), and all containers must fit in a single quart-size clear bag. Most travel bottle sets are sold in 2 oz or 3 oz sizes to stay safely under that limit; r/onebag commenters often recommend the smaller 2 oz size because more of them fit into a quart bag than 3.4 oz bottles.