This is a standard mil-spec flat top M4 upper receiver with engraved T markings. These are made from 7075-T6 forgings to mil-spec and hard coat anodized. The inside of the receiver also has a dry film lube per Mil-Spec.
This receiver features M4 feedramps. Note: DO NOT use a barrel that does NOT have rifle feedramps with this upper receiver. It will create a ridge causing feed problems. Most ALL barrels have the Feed Ramps so this is rare but check to be sure.
A-3 Stripped Upper Receiver does not include fwd assist, and ejection port assembly.
Complete comes with Fwd assist, and ejection port assembly installed.
More information about the difference of A-3 and A-4 upper receivershere.