someone said not interchangeable parts? not sure how they figured that since all parts between my r1 and springfield gi seem pretty interchangeable. The extractor from the factory worked, but would not extract live rounds unless they were very very short. A hardcore extractor fixed that, no fitting, just dropped in. Thats my only complaint. The new extractor is slightly below flush, but not too bad. The Grips are very well made, and from a good pattern or wood on mine. Finish is very good. Fit could be better, but is still decent. The sights will work themselves loose after a few hundred rounds, so youll need to locktite them down when there sighted in. My barrels are interchangeable.