internal hub

I have been keeping an eye out for one of these for a while now but they don't seem to pop up very often. But I just stumbled across someone selling a bunch of them cheap. I honestly don't know much about them in general so is there anything I should keep an eye out for? I'm planning to head...

Today I was cleaning and servicing some hubs I've acquired along the way This type I never worked on before...it's a very smooth operating hub I may use in a future build Shimano 3 speed Hub Cartridge Type I take it its an internal 3 speed hub I've worked on the ones with the little chain...