#html-body [data-pb-style=OIHHGK4]{justify-content:flex-start;display:flex;flex-direction:column;background-position:left top;background-size:cover;background-repeat:no-repeat;background-attachment:scroll}These exclusive retro uppers are a throwback to the late 60's era 604s that features a grey anodized slick-sided upper receiver with a 20" parkerized 5.56 NATO barrel. The rifle length gas system and C158 BCG are paired to ensure smooth cycling and maximum durability. The later model 604 rifles also featured a mil-spec "birdcage" style A1 muzzle brake rather than the 3 prong brakes used on the previous versions. These complete uppers are hand fitted and assembled right here in the United States of America.