2 Black circles moving in a straight line.

As I was walking out of my house I checked the time, it was 7:52pm.  I was taking out the garbage. Once outside I glanced toward the western sky and saw what I first thought was a large black bird(buzzard)gliding through the air on wind/thermal current. As I continued to watch I noticed it was moving in a straight line, no wing flaps, no variation from the southwest to north east direction it was moving.  I realised that it was no bird and thought maybe a ballon. It was a black circle moving in a straight line.
I then realised that it could not be a ballon, because there was no deviation in it's path, i.e. no floating or oscillating movements as baloon would with wind currents. I then quickly went inside to get my binoculars. Back outside I focused on the object.
I noticed it was solid black, not reflecting any light at all. Kind of a flat black if you will. It was also a perfect circle! Not egg shaped like most baloons being round at the top and more narrow at the bottom.  Anyways I as watched through the binocs it had nothing attached(i.e.string)no lights, no markings whatsoever. I would guess it was about 2-3k feet up, making no sound at all. The thing that puzzled me so was that it flew in a straight line, never deviating from it's path. I watched for maybe 3 mins until it flew out of sight in the distance.  It was moving around 25-30 mph. Not very fast at all.
Well I go back inside wondering what I had just seen, when I decided go back out to make sure I closed the lid on outside garbage. I still had binocs in hand. While outside I looked back to the area where I first spotted the circle and lo and behold there is a second one exactly like the first moving in the exact same manner and path as well as speed.  I estimate these thing were no more than 2-3 feet wide. I checked the time and it was 7:56pm. I also watched this object through the binocs until it flew out of sight. It looked identical to the first object.
I went back inside and checked local weather radar on cable TV. The winds were light 3-5 mph out of the southeast. If it were big ballons they would have been traveling in a straight line against a cross wind! I have no idea what I saw, but I know what they were not(bird,or baloon). The Sun was setting but there was still plenty of daylight.  Weather was clear with light clouds. These black circles stood out very well against the sky. If anyone had been in our area and looked up they would have easily spotted the objects. I know people see alot of things, some explainable, some not. But two perfectly shaped circles, black, travelling in precise straight lines with no deviations in their path is really weird. Again, no sound, no smoke trail,no strings, lights, reflections, markings, nothing. I am a 47yo Operations Manager who lives in Beaufort S.C. We have 2 major airports, Hilton Head, SavannahG.A., as well as the Marine Corp. Air Station, so I see lots of private, commercia! l, as well as military air craft. These objects were truly something I have never seen before.