There are a wide variety of yoga blocks on the market in various shapes and sizes. However, a standard yoga block is about 4" x 6" x 9”. Iyengar yoga is one of the most popular forms of yoga that uses tools to support the body, and this means there have been many different blocks developed over the years. If you practice Iyengar yoga, you will find that the recommended size is 9" x 4.5" x 3", so slightly smaller and narrower than a standard yoga block. Depending on the size of your hands, you may find a slightly bigger or smaller block makes it easier for you to work with. Yoga blocks do also come in different shapes, although some people refer to them then as bolsters or cushions. However, you can get curved, egg-shaped or rounded blocks which are perfect for backbends as they are ergonomically shaped to support your spine.