Great product! - Nordic Components AR15 Extruded Flat Top Picatinny Rail NC15 Stripped Upper

The other reviewers apparently didn't actually know what they were purchasing. It is not a standard mil-spec receiver, so do not expect handguards that rely on mil-spec dimensions for anti-rotation tabs to fit. This is an extruded upper, not forged or billet, and as such it is intentionally meant to be thicker, heavier, and more rigid than a standard upper. This is perfect for building a varmint, precision, competition, or other such rig. The machining and finish is very nice, and the weight and rigidity of this definitely feels like it'll serve well for an accuracy build.

It receives four stars from me for one reason, and that's the barrel extension fitment. For a precision upper I'd like a very tight fitment (such as the BCM uppers), though this one is a bit loose on my White Oak Armament upper. This can be remedied one of three ways - if you're having a barrel built, get the BAT Machine oversize barrel extension and you'll be just fine. If you're handy, you can get some feeler gauges and shim stock to cut and fit to your barrel extension and that will get you a nice tight and centered fit. If you're less handy/patient or just cheap like I am, you can use Loctite 609 or 620 to bed the barrel in the upper (I've got 609 waiting for me tomorrow). This is what I'll be doing and also what Criterion recommends. There's plenty of videos and guides out there for both shimming and bedding methods.

It's a self-fixable error, but if this had a BCM style fit requiring me to put the barrel in the freezer overnight and hit this with a heatgun to get the barrel in, that'd push it to a 5 star for me. Otherwise, I'm still exceptionally happy with this upper and looking forward to getting it assembled, punching tiny holes, and smacking steel.