Likely the best adjustable gas block on the market - Riflespeed Gas Control .750in Assembly Block

The fit and finish of the gas block is exceptional. As others have said, you will need to buy their straight gas tube to make this work. I ordered the 4.8 inch model as I am using a 12.6" hand guard. There is a sizing tool that's fairly accurate on the manufacturer's website. I won't get into the adjustments, but the item comes with two plungers, a standard one and a more restrictive one. If you buy the gas tube, you will have two assembly roll pins. There are two methods to affix the block to your barrel. One method is a pin which will require modification to the barrel and the other is two set screws. With a 12.6" hand guard, the control knob sticks out roughly two inches. The only thing I would change from an engineering standpoint is a more positive clicking detent. You can buy an assortment of control knobs from their website for about $80-90 apiece. I believe Opticsplanet carries them too.