I got this cactus as a present, at least I think it is a cactus, but don't know what species it is. It is small now about 5-6 cm in height. It has hairy or woolly sides, and has multiple stems. Does anyone know what species it is, and how big it can grow? Thanks in advance.
Someone told me that this cactus is Cereus forbesii. I think it looks very similar, see here.