Rail Integration System

Rail interface system or rail integration system (RIS for short, sometimes also referred to as rail accessory system, RAS) is a generic term for a standardized rail system for attaching accessories to small firearms such as pistols, rifles and light machine guns. Such accessories commonly include tactical lights, laser aiming modules, forward hand grips for improving weapon handling, telescopic sights for long-range targets, and reflex sights/red-dot sights for short/medium-ranged targets, back-up iron sight, bipods/tripods, and bayonets.
Type.
Most RIS equipment is compatible with one or more of the most common rail systems, all of which are broadly similar:
These are used primarily in the military and by firearm enthusiasts to improve the usability of the weapon, being accessorized quickly and efficiently without requiring the operator to field-strip the weapon. Basic systems such as small rails (20mm is standard) with holes machined in them to be screwed onto the existing hand-guard of a rifle and can cost as little as US$25 to US$40. More advanced systems allow for numerous accessories to be mounted simultaneously and can cost upwards of US$200.