Available in 4-inch, 6-inch, 250-mm, 10-inch, and 400-mm sizes, the VHS series pumps are the fastest and cleanest diffusion pumps of their size available today. The VHS series patented Bulge Contour doubles gas capture and maintains lower pressure. All VHS series pumps have sight glass/fill and drain assemblies for continuous monitoring and easy maintenance of pump fluid. Finned boilers increase surface area, prolonging pumping fluid life. Full thermal protection and quick-cool coils are also standard. The 4-inch, 6-inch, and 10-inch pumps can be ordered with ASA or ISO flanges, standard or extended cold caps, and a variety of voltages.