(This plant comes in a 3.5 inch pot. You will receive a very similar plant to the one in the picture. It may or may not be blooming at the time of your purchase. The plant is shipped in its pot to prevent any damage to the roots).
Notocactus werdermannianus is easy to grow. It likes a warm bright location, does great in partial shade but doesn't like full, hot blazing sun in the central summer month. Can support quite some water during the growing season but pot plants in winter are wet-sensitive and needs to be kept dry (rots easily if soil is wet and cold) tends to lose its roots in winter. Usually it is recommended to over-winter this plant in a bright and warm greenhouse with at least 8-10° C , but it has proved to tolerate temperatures as low as -5° C for short periods.
Some of the information in this description has been found at desert-tropicals.com, llifle.com and cactus-art.biz