Gitzo "Embase" tripod hub adapter, 3.25" OD at the top, fits into a 2-3/4" hole on the top of your Gitzo tripod, 3/8" threaded post. 

WHO WE ARE: Oddog2 is a husband/wife team, home-based small business specializing in the buying/refurbishment/selling of primarily photographic equipment. We do occasionally have other types of things to sell that come to us as a result of our search for camera-related items. We have over 50 years of experience with photographic equipment, both as a shooter (17 years newspaper photojournalist) and as a collector/restorer/seller. We have been on eBay as Oddog or Oddog2 since September 1999.