stock is a stock is a stock, right? Well, no. One factor that makes the AR-type rifle so attractive is that the term “AR” or “Modern Sporting Rifle” really doesn’t define a specific gun but rather a platform on which rifles can be designed and configured. Everything is customizable: caliber, barrel length and type, trigger, stock, handguard, sighting options, and muzzle devices. You get the idea. When it comes time to choose the right buttstock for your AR rifle, the first step is to narrow down the functional type. For example, you can choose a fixed stock, a collapsible stock, an adjustable stock, or maybe a minimalist design that emphasizes lightweight and low profile. Let’s take a quick look at some of the best options available. Be sure to get the right size buttstock for your rifle's buffer tube. Diameter AR buffer tubes come in two sizes: commercial or mil-spec. If you're not sure which you have, break out the calipers. Commercial buffer tubes have a diameter of 1.168"while mil-spec tubes are slightly smaller with a diameter of 1.148". That difference doesn't sound like much, but it's enough to keep the two from being interchangeable. Length Additionally, be sure to consider the length of your receiver extension (buffer) tube when choosing a stock. There are two lengths: rifle and carbine. Originally, back in the M16 days, the idea was for the rifle to have a fairly long length of pull (receiver tube and stock length) to support a bladed stance. As body armor and shooting tactics evolved, the carbine stock was phased in to support a “front forward” position where body armor would be most effective. The rifle-length tubes are generally round while the adjustable carbine tube have a ridge with the different locking positions. One more thing. Since the receiver extension tube also houses the buffer and spring, you need to match that too. There are rifle-length and carbine-length buffer and spring sets. As long as you match all four components, stock, tube, buffer, and spring, you should be good to go.