Buy 4 ($99) With 4 SitBlox you can sit more upright with knee and hip support as well as give you additional kneeling options.
Buy 2 ($49) If you already have a tall seat cushion you're using you could buy 2 SitBlox to help you support your legs while sitting cross-legged. If kneeling is your thing you can stack two and adjust the height.
With four SitBlox there are over many ways you can sit to allow you to drop in to your meditation and easily find your "calm".
Made from the same stuff as foam yoga blocks this meditation "sit system" was design people looking for a more supportive way to kneel or sit cross-legged.