Astrophytum asterias is a small spineless cactus that resembles a washed ashore sea urchin. The large flowers are yellow and usually are produced right after periods of high humidity in the summer. It likes bright light and a warm location during summer. Water it moderately in the summer and keep dry in winter. You are selecting the plant size pictured. 

Unless otherwise noted in the description above, all live plants are shipped without soil and pot, also known as bare root.