Used set of LT1/LS1 fuel rail quick connect/disconnect fittings.  This is both a feed (3/8") and return (5/16") setup, commonly used with the LT1 fuel rails.  These ends allow you to use a standard hose when plumbing your engine swap.  These are OEM ends that the factory would use in production hoses. You can either use plastic nylon tubing specific for this fitting, or you can use high pressure rubber fuel injection hose (3/8" or 10mm) and (5/16" or 8mm).  These will fit factory 92-97 LT1, 97-98 LS1 and 99-05 LS truck fuel rails.

The item in the picture is the actual photo of the item being sold.