I have no idea. Depends on the quantity of tritium, quality of the phospherous (Iknow this isnt spelt right) coating etc

The small one is a bit biggerthan the one I have experience with. About 1.5 inches. I have walked around at night using it.

Its like using a half flat battery with a LED and it gave the colour of the glow inthe dark hands of my Seiko watch. but the colour will depend on the phosphorus used.
Enough light to walk around with but you had to hold it close to make out details.

Had to be there, its hard to explain, but I was impressed with the amount of light from its size.

Edit:
I had another look at the Website before I closed it, and I realised I was working on overall dimensions. The size of the small one is about the size I was dealing with.