I used the flex cup for several years and thought switching from tampons to a cup was lifechanging. But after trying the flex disc, I'm never going back to anything else. I don't feel it at all, it works even better than a cup, and has saved me so much money and waste from no longer needing to keep getting tampons.
My only "complaint" would be that I wish they offered the disc in black like the flex cup because it stains very quickly. But that's just a personal preference and I can't recommend this product highly enough.