This is a CNC machined version of my hop up arm for the Action Army VSR-10 chamber. Design is exactly the same as the 3D printed version that I've had available for years. Benefits of the CNC version: stiffer, more durable, can use standard AA spring return. Also, it just looks really nice. Quick synopsis of why you'd want an arm like mine: being a one-piece design we remove a moving component in the hopup linkage, thus increasing shot-to-shot consistency (sometimes drastically). The built-in nub is a concave design that fully fills the AA chamber window - making the most use of your bucking. Nearly everyone that has used (the 3D printed version) has reported positive effects in their shots. Now, with the CNC machined version, I can add long-term durability to the list a positive attributes. If you need more than one, send me a message. airsoftMarshall/Masada