1989 Osyssey Aerator Seat Post / Pump.  NOS in the original package and perfect.  26.6mm diameter, 300mm length (230mm from minimum insertion line to center of rails).  Innovative seat post that doubles as a Schrader pump, and a Presta as well if using a simple adaptor.  450 grams.  Perfect for your Jamis Diablo, Schwinn KOM and Cimarron, Specialized Team Stumpjumper, Mt Shasta Pachanga, Redline Conquest 3 and other mountain bikes.  Also would work well on your Motobecane, Cilo, Allegro, Mondia or other French/Swiss road bike that takes a 26.6mm post.  Buyer to pay $10.00 USPS Ground Advantage shipping with tracking.  Buyers outside the Continental US to use Ebay's International Shipping.  Thanks for looking!