Pillow that is made from rubber like a bicycle tube. Very durable but I had a lot of trouble inflating it, it needs a pump and still I couldn't manage to secure it. There were no instructions as simple as it may seem. As much as I managed to inflate it and sit on it, it was difficult to be comfortable because fully inflated it is not comfortable and if it is less inflated it makes you sway a bit back and forth...

It served me very well. With this, I no longer have a problem sitting for a long time. I don't know how the problem with the coccyx was created, but the cushion helps. The only problem is that now that it's summer, I sweat a little.