I recently purchased an aim surplus nib-x EXO BCG. For just over $100 I didn't know what to expect. I know aim sells a lot of bcg's but I wasn't convinced of the quality. After getting it I can now say that the quality is amazing. The fit and finish is excellent. The gas key is staked very well and everything is done right. Fits perfectly in my Ruger AR556. I can't wait to test it out and see how well it works. The finish isn't the typical nib-x finish. It's more of a dull silver. Supposedly from the EXO coating. For the price this thing costs I can't see anything being much better. If it holds up it will be an amazing deal. And with a great warranty I don't think you can go wrong with it.