Rare and best kit made for the AR 15. The Adams Arms Piston System: A short stroke free floating piston system. Is Self-Cleaning. Carbon and gases are expelled forward, away from operator. Corrosive resistant coating processes. Harmonics are not transferred into the barrel. Adjustable gas settings for various applications. Doesn't vent directly to atmospheric pressure; this eliminates flash signature and super sonic crack which is optimal for night vision and suppresses fire. This system requires a carbine gas length (7.866" from barrel extension to shoulder) and a .750" gas seat. We recommend using a standard barrel nut or barrel nut with similar measurements for proper fit and function of the kit. These were $325 new SELL $250 firm

Specifications for Adams Arms CPSDADA AR-15 Gas Piston Kit Carbine10"-16" Length. 75" Diameter:
Mfg Item Num: CPSDADA
Supplier SKU: 68148
Category: FIREARM PARTS
Type: Gas Piston Kit
Model: CPSDADA
Finish: Black
Size: Carbine

Check out this link and the video there.

https://www.opticsplanet.com/adams-arms-cpsdada-ar