I had heard of the Natu, which seemed like a Si-bell rebranded, but in my searching I also saw a picture of a slightly different cup. It had some subdued rings at the base which was also a little more pointed in shape, and had a stem with rounded balls for grip, not the harsh rings I had found so uncomfortable. This could be a perfect cup! A slightly better shape for me, and a smoother but still grip-able stem. So, here it is:
The silicone is smoother/shinier and therefore also more slippery, but I find this helps it glide in and out more easily, though I have lost my grip on it and dropped it (luckily not in the toilet!). It is maybe a hair softer resistance (possibly a little thinner walled) than a Si-bell. I did have to experiment with some new intricate folds for this one. My go to punch down and 7 folds just didn't pop it open consistently. I have to do a 'origami' fold of sorts:
The mold seams are not as perfectly finished as some cups, but I have not needed or desired to modify the cup in any way. The suction release holes are very well finished.
Here are some comparison photos:
With a Lunette, both small sizes
and a small Sckoon
Overall, the Natu is my favorite cup for comfort. It's soft enough for my first crampy/sensitive day and it doesn't put pressure on my bladder like other cups. It's unique design features that make it slightly different than a Si-bell make it just perfect for me.