For cylinders up to 1" diameter bore.

This lubricator should be attached to the steam chest or fitted to the steam line close to the engine by a tee. 
Opening a needle valve lets steam pass into the lubricator. Steam condenses in the lubricator and sinks to the bottom. The oil is displaced by the water and passes into the steam line, lubricating the engine.
The lubricator may be refilled by closing the needle valve, opening the drain valve to remove water, and removing the cover plug to refill with oil.
 Body is ⅝" diameter, total height is 2", threaded 3/16-40, made of brass.