Base Model Specs *Due to the state of the firearms market, many of our options are out of stock and stock may fluctuate quickly. We are doing our best to keep option availablilty up to date, and what we show on the website as an option is all we have to offer. Occasionally, an option may sell out before we can update stock, and you will be notified of that so we can discuss alternatives. Thank you for your patience and understanding.*--Centurion Arms 16" Lightweight Midlength CM4 5.56mm hammer forged barrel 1 in 7" twist extra thick chrome lining and barrel steel specifically engineered for machine guns for longer life (most all hammer forged barrels on the market are not made of this steel).--Upper receiver is standard forged Mil-Spec with M4 Extended feed ramps--Centurion Arms low profile pinned gas block--13" MLOK Centurion Arms CMR Rail--Mid-length gas tube --Standard A2 Flash Hider Options (when in stock, available, and compatible)--14.5" and 13.9" Lightweight Midlength CHF Barrel--Centurion Arms 9", 10", 12" C4 Quad Rail--Centurion Arms 9", 10" & 15" MLOK CMR Handguard--Auto bolt carrier group with MPI tested bolt--Standard charging handle or PRI gas buster charging handle--Surefire Warcomp, Surefire SMB Muzzle Brake, Centurion Arms 9315 Open (3 or 4) Prong Flash Hiders and Centurion Arms 6315 Stoner 63 Flash Hider--Backup Iron Sights - Folding Micro Front and Folding Micro Rear (300M) Price for Base Upper with Standard Specs $895.00****Not all items shown in pictures are included with purchase. Uppers may be shown on lowers as full rifles.****