8×25

8x25 is a designation that can refer to several different things, most commonly ammunition and optical devices.

In the context of ammunition, 8x25 typically describes a cartridge. The "8" denotes the approximate bore diameter of the firearm in millimeters, which is roughly 0.315 inches. The "25" indicates the length of the cartridge case in millimeters, which is 25 mm. This particular caliber is not as common as some other pistol or rifle rounds, but it has seen use in various historical and niche firearms. Examples might include specific revolvers or automatic pistols designed for this size of ammunition. The performance characteristics of an 8x25 round would depend on the specific projectile weight and design, as well as the firearm it is chambered in.

As an optical device designation, 8x25 refers to magnification and objective lens diameter. The "8x" signifies that the binoculars or scope magnifies the viewed object eight times its actual size. The "25" indicates the diameter of the objective lens in millimeters, which is the lens at the front of the device that gathers light. Therefore, 8x25 binoculars would provide an eight-fold magnification with a 25mm objective lens. This combination is often found in compact and lightweight binoculars, making them suitable for casual use, birdwatching, or travel where portability is a consideration. The larger the objective lens diameter, generally the brighter the image, especially in low light conditions.