Description from Aero Precision: 
 
"Due to a contract overrun, our M5 .308 Complete Uppers with an Adjustable Gas Block are up for grabs! Experience the flexibility to tune your gas system to your exact needs, enhancing the performance and adaptability of your rifle. With the adjustable gas block, tailor your shooting experience with precision."
 
These also include contract overrun dual ejector BCGs and milspec charging handles.