yes. stag makes great uppers. infact, for those of us "Left handed" folk in the world, they even offer fully-built left handed upper receivers. but otherwise, they are fantastic no matter what upper you get.
this is where things might get confusing for you. have you determined what kind of sights you want to use?
how about length? purpose?
let's start with basic uppers.
a basic 16 inch upper, "Stag-15" AKA 1H Model. if you are building a classic style rifle, M16a1 style, this is what you want. it's your no-frills classic upper, with front and rear sights included. the rear handle is removable for BUIS or other accessories.
http://www.riflegear.com/p-45-stag-arms-model-1h.aspx
however, if you do not like the rear sight setup, or perhaps want to spend alittle less? then look into the stag 2h model. the basic difference is the rear sight is a BUIS (Back up iron sight) instead of the classic carry handle. it is better for the use of optics or scopes, however the front sight stays the same.
http://www.riflegear.com/p-46-stag-arms-model-2h.aspx
if you are looking for a real custom build; involving quad rails, flip up sights, and eventually a scope, then look into the stag 3H model. this unit, like the others, is a flat top but comes with a picatinny rail gas block. so it is ready for a scope or other optics, and the iron sights wont interfere with the view. but, you must purchase them seperately, which accounts for the lower price. at 430 dollars its the most affordable upper
http://www.riflegear.com/p-48-stag-arms-model-3h.aspx
there are many other companies but most are more expensive and about equal to stag. LMT, RRA, DPMS, CMMG, & Double star.
