The Fulton Armory system is a reciprocating side charging system. You have the option of using the rear charging handle or the right side charging handle.
There are companies that make a left side reciprocating handle as well. It looks very similar to the Fulton Armory version. LAR Grizzly used to make a dual side charge upper, with no rear charging handle.
On top of it all, there are the left side non-reciprocating handles. American Spirit Arms, JP Enterprise, SWORD Int... just to name a few. These uppers generally do NOT have a rear charging handle (I believe the JP version has a rear handle still).