1. Is the cushion comfortable? I'm thinking of using it on a regular hard chair, what do you think?
Our ROZI cushion has an overwhelming fluffiness, so you can double the effect of using it with a hard chair. 

2. I want to give it to my friend as a gift, how big is it?
You don't have to worry about it. The cushion size is 45*40 and is not a small-size product.

3. My sitting posture is not good, can it help correct my posture?
First, it helps to correct the posture like the product name. It has hip support and a standing angle, which can support the hips as a whole and keep the waist and spine upright.