平衡墊

I keep it on my office chair and my lower back feels way less stiff by the end of the day. Inflating it took a couple minutes, and the little bumps on the surface give a decent grip so it doesn't slide around.

It took a few days to get used to the slight wobble, but now my back feels way less stiff after hours at my desk. I mainly use it to keep my core engaged while I work.

Bought this to fix my slouch at my desk and it does keep me sitting up straighter, though the pump it came with feels a bit flimsy. Inflating it took some effort to get the firmness right, but once there it's surprisingly comfortable for a full workday.