These Welch 2561B-50 laboratory duty dry oil-free dual stage piston vacuum pumps are perfect for many common laboratory vacuum applications. The 2516-50 produces and ultimate vacuum pressure of 5 Torr (29.8 inches of Hg) and includes a vacuum regulator with a built in vacuum gauge which is simple to adjust & monitor the vacuum level. The 2561B-50 WOB-L pump includes an inlet water trap with float ball that rises to seal off the vacuum pump in case of accidental ingestion of water and a muffler which quiets the pump and filters discharge air. These Welch 2561B-50 WOB-L piston pumps operate on 1-Phase 110 to 120 VAC at 50/60 Hz and are designed for use with dry or aqueous vapor applications only. A user's instruction manual in PDF format is available for downloaded below.