There are several manufacturers of 308 caliber AR-family rifles now. Most of them will interchange with one system or another, but it can be tough to keep track of which one is which. While many components are the same, for intstance, your 308 standard lower parts kits, the design of DPMS style upper and lower can vary greatly. Previously, I had described the differences in 308 DPMS styles, however let's address major manufacturers compatibility.
Aero Precision - Design is taking after Armalite AR-10. Your standard high profile 308 DPMS style
Bushmaster - designed their own lR 308, then lost interest and sold it to RRA
Rock River Arms - continues with their own design, usually high profile
Noveske - high profile, very much like Aero
CMMG - low profile, usually, some machining is required for other compatibility
Moriarti Armaments - your true low profile design