If a menstrual cup is too firm, it can be uncomfortable, and if it is too soft, it may leak or make a mess when removing it. VOXAPOD cup is made with thinner and softer cup walls to contour and move with the shape of your body, while the thicker and firmer ribbing is strategically placed to help the cup open, form seal, prevent leaks, and break the seal for a more comfortable and mess-free removal (ribs are aligned with suction holes so when you pinch at the base it breaks the seal at the top of the cup). Our medium cup is slightly thicker and firmer and designed for those with a heavy flow or that have weaker pelvic floor muscles and might need more resistance to create a good seal and stay put, while our small size cup is slightly softer because of its size and thickness. Most users can use either size cup, but we do recommend our small size for first-time cup users.