These are Gen 1 Tromix billet upper receivers with large ejection ports for use with 458 SOCOM, 375 SOCOM, 50 Beowulf, 450 Bushmaster, etc.
The receivers are stripped, ie no forward assist assembly and no ejection port cover.
Dimensionally, these receivers are fine, but the black anodizing process did not go as planned, so the finish looks rather poor.
These are Gen 1 receivers that don’t have the relief cut behind the barrel nut to allow hand guard “wings” to extend rearward of the barrel nut.
You would need to use a hand guard that flat/square at the rear.