The Armaspec Stealth Recoil Spring is one of the best upgrades you can make to your AR-15 to make it quieter. This multi-stage drop-in replacement for your standard buffer spring eliminates the noise from your action rattling around the receiver extension and keeps the bolt carrier group's buffer from rubbing against the inner wall of the buffer tube, which reduces felt recoil significantly.
The SRS is also a lot easier to work on than traditional buffer systems. Changing the buffer weights on a standard unit requires loosening a screw that is a little tricky to get at, which can be done by loosening a 3/32" hex screw at the rear of the SRS and rotating it counterclockwise to separate the end from the guide rod, but this is a pain and not something you want to do every time you need to change the buffer weights on your rifle. The SRS has a cross hole drilled in the guide rod which lets you use a hex key to remove the screw from the opposite side of the unit, making it much easier to loosen and remove both the buffer base and the buffer weight.
The SRS can be installed with or without a buffer retainer and is compatible with AR-15 rifles with carbine length buffer tubes. It is self contained and has a rubber O-ring on the head of the buffer mass to save metal-on-metal contact and the springs are captured so they do not rub up against the walls of the buffer tube. It is a very smooth and quiet system and is made in the U.S.A.