https://coltparts.com/colt-6943-556-monolithic-upper-receiver-assembly-11-barrel/
Colt LE6943CK 11.5 inch Monolithic Upper Receiver Assembly
The Colt LE6943CK Monolithic Upper Assembly feature's Colt's new monolithic upper receiver. In addition to an uninterrupted full-length front rail, this upper...
upper receivercoltinchmonolithicassembly