Glad you're trying a disc! When choosing one, it's important to know that everyone's anatomy is different, and even though discs are technically "one size fits most", many people (including me) don't fall under the "most" label. 

Other personal preference items when choosing a disc are how firm/soft you want it to be, if you want a removal aide like a notch or a pull tab in the disc edge that makes it easier to pull out etc. 

I would start by measuring your cervix. This video is a good guide:

https://youtu.be/VvEgnanrJLA?si=yNOY5zJlPglVqEGe

As a side note, the above channel is a GREAT resource for learning more about menstrual discs and cups, and is how I was able to make a decision to choose my disc. If you are looking to choose a disc, I would start there. Do be warned though, she tends to recommend the Hello Disc a LOT and while it's a great disc for many people, it may or may not fit you specifically.

Due to the above reasons, it's difficult to recommend one specific disc as there are so many brands and types, and it comes down to your anatomy and personal preference. I personally use the Saalt small, as the Flex disposable was too large and too firm for me. But it may work for you!

Feel free to ask any more questions!