2ml & 3ml: For a quick test without needing to spend more on bigger sizes incase you don't end up liking the perfume. Or you need a perfume for a one night/day occasion, these sizes are perfect.

5ml & 10ml: Best for longer testing or if you want to use more than one perfume while not having to worry about running out of something to use very quickly. One of these sizes should last you a week or two based on personal use and amount of sprays per use.

30ml: You found your signature scent? this size carries around 500 sprays and will get you covered for months.