if its the smaller of the 2 you need, be prepared for a £100 odd cost! the rubber mouldings on the pump end of these going rotten is a common Miele problem and often only show up after you have disturbed them by removing the circ pump so I always warn customers of the consequences before starting work as I sure would not want to foot the bill for those.
if you are changing it because the rubber on the end has rotted, would suggest you take a good look at the thicker one next to it too, usually if one has gone the other is in a similar state. and, as warned, that part is not cheap! part number for the thinner one (140) is 6001202