What f-stop would this pinhole lens be?

Http://www.ebay.com/itm/260800576377

It's 0.25mm sized hole, and i don't know if that is really a "pinhole" or more of a "f/32"… Because isn't a real pinhole like f/165 or more?

It depends on the focal lenght; for 0.25 mm pinhole it should be 50 mm, so that's f 200. But if you mount it in a nikon, the distance between the pinhole and the film will be shorter; divide it by 0.25

The "pin-hole" in the lens you are looking at is not the central darker area you can see; this is just the holder for the "pin-hole" element. I believe this pin-hole lens is actually advertised as f/175.

Regards the earlier reply, you have to understand how a pin-hole lens works. The idea is that the aperture would ideally be infinitely small such that there's no focal point, no minimum focal distance, and no maximum focal distance. And if you find that confusing, I have a zone plate lens too!

It is dependant on the focal length.

The f-number is determined by dividing the focal length by the diameter of the opening.

So a 50mm focal length divided by 0.25mm would give it an f-stop of f/200.