Well, the bren is almost a clone of the scar. Almost, but it has a machined aluminum upper vs the extruded scar upper. The gas system of the bren has an exposed gas system and more parts. CZ advises an armorer disassemble the bolt. The bren's stock has no locking tab for side folder. The bren is heavier. The bren's pistol grip has interchangeable backstraps, but cannot be completely replaced like the scar. I may be missing some more, but I'm sure someone will be along shortly to correct me.