ROWUK, OK, there are sealed ball bearings at each end - between the shaft and the housing, I assume. While this certainly assures a smooth rotation, there must be some clearance between the carbon fiber valve and the red brass cylinder, otherwise I'd expect it to bind with the slightest introduction of dirt. So, presuming there is a small clearance, without oil to seal between the two surfaces how is air kept from leaking. Is the carbon fiber so slick it needs no lubing? On a piston horn, that clearance is sealed by the lubricating oil, enough so that air won't leak, unless the valve is heavily worn. veery PS Thanks for countering my levity with your gravitas! I guess you would be the "straight" man.