2 car trailers are trailers that can carry 2 cars utilizing a single tow vehicle.  Generally speaking these trailers come in 3 varieties, enclosed gooseneck, open gooseneck or bumper pull stacker trailers.  The 2 car stack trailer will include a lift and one car will be raised above a second.  2 car trailers also include a tie down system that will have a minimum of 6 tie down points, but often more.  E-Track is a good idea if the cars you will be hauling are different sizes.  A 2 car stacker trailers normally are a minimum of 24 feet and come as long as 34 feet.  Enclosed goosenecks are generally a minimum of 44 feet long, but can be as long as 53 feet.  Open goosenecks can range in size depending on their design.  A flat bed will generally start at 44 feet long and range up to 48 feet long, while an over the cab model can be as small as 40 feet.  A stacker or enclosed trailer is generally recommended due to the protection they provide from road hazards during transport.