When shopping for a rifle scope, there are several key specifications to consider to ensure you get the best scope for your needs. Magnification determines how much the image of the target is magnified when viewed through the scope, with higher magnifications being useful for longer distances but also making it harder to keep the crosshairs steady. The size of the objective lens, located at the front of the scope, determines how much light can enter the scope and affects the brightness and clarity of the image. The reticle, or crosshairs, inside the scope can come in various types such as duplex, mil-dot, or BDC, and each has its own set of features. Eye relief refers to the distance between the eyepiece of the scope and the shooter's eye, and a longer eye relief is beneficial for recoil-heavy firearms. Parallax is the phenomenon where the position of the reticle appears to shift in relation to the target as the shooter moves their eye, and adjustable parallax allows the shooter to fine-tune the scope for the specific distance of the target. Durability and construction are also important factors to consider when shopping for a rifle scope.