If going the lightest weight possible without sacrificing quality or reliability then get this - V Seven AR-15 Enlightened Upper Receiver, 2055 Lithium/Aluminum

Most AR15 owners out there probably can’t justify themselves into spending $350+ on this upper receiver when their $65 “anderson upper does the job enough” for them. But if you are like me and enjoy building ultra light weight AR15’s as one of your AR15 hobby’s or just want a top of the line upper pr want something to show off at the range then this may be what you are looking for. V seven makes top quality stuff, I own a good amount of their products including their sister company’s dark hour defenses products also. This is one of the lightest alloy uppers out there besides maybe a few others but some of those require you to buy the upper and lower as a set and none are going to be as light and as strong as this one made from lithium aluminum.
The anodizing is more of a matte type, I’m assuming due to the type of alloy used compared to 7075 or 6061 aluminum anodizing so might be difficult to find exact a matched anodized black lower that matches this ones anodizing besides the v seven 2055 lower. I cerakoted my whole ar15 that i used this on so the anodizing was no issue for me but might be for others that care if the lower and upper might be slightly different tones of black if used with a different lower other than v sevens 2055 lower.