How do I know which Aneros toy to get?

How do I know which toy I should get? There’s various different shapes and sizes, but I don’t know which one is more likely to work for me. The website “suggest a toy” is mostly for how experienced you are with prostate play, nothing else. Do I need to find and estimate where my prostate is then make a guess on what to get based on that? How did you choose which to buy?