This is an "O-ring" style for Harley-Davidson Panheads (or Knuckleheads which have had the O-ring conversion). I did find an issue where chrome is peeling near where the o-ring sits however I do think it will seal well once cleaned up. The item "Harley Davidson SU Carburetor O Ring Intake Manifold For Panhead or Knucklehead" is in sale since Monday, July 20, 2020. This item is in the category "eBay Motors\Parts & Accessories\Motorcycle Parts\Air Intake & Fuel Delivery\Air Filters".
The seller is "barnfiend" and is located in Buffalo, New York. This item can be shipped to United States, Canada, United Kingdom, Australia, Mexico, Germany, Japan, Denmark, Romania, Slovakia, Bulgaria, Czech republic, Finland, Hungary, Latvia, Lithuania, Malta, Estonia, Greece, Portugal, Cyprus, Slovenia, China, Sweden, South Korea, Indonesia, Taiwan, South africa, Thailand, Belgium, France, Hong Kong, Ireland, Netherlands, Poland, Spain, Italy, Austria, Bahamas, Israel, New Zealand, Singapore, Switzerland, Norway, Saudi arabia, United arab emirates, Qatar, Kuwait, Bahrain, Croatia, Malaysia, Chile, Colombia, Costa rica, Dominican republic, Panama, Trinidad and tobago, Guatemala, El salvador, Honduras, Jamaica, Antigua and barbuda, Aruba, Belize, Dominica, Grenada, Saint kitts and nevis, Saint lucia, Montserrat, Turks and caicos islands, Barbados, Bangladesh, Bermuda, Brunei darussalam, Bolivia, Egypt, French guiana, Guernsey, Gibraltar, Guadeloupe, Iceland, Jersey, Jordan, Cambodia, Liechtenstein, Sri lanka, Luxembourg, Monaco, Macao, Martinique, Maldives, Nicaragua, Oman, Pakistan, Paraguay, Reunion, Uruguay, Russian federation, Philippines, Ukraine, Cayman islands.