I recently received my new (to me) 4 inch oil diffusion pump from sunnking on eBay, and wow! this thing is a monster! This is a 4 inch water jacket oil diffusion pump from a scanning electron microscope, complete with accessories, I am unsure of what they all are, but there is a large reservoir, a pirani gauge, and some sort of piston and micro switch. More research is needed, as the pump just arrived. I plan to use this pump in the future for some hardcore projects, including a very large Farnsworth–Hirsch nuclear fusor.