and available as aftermarket add-on parts for most actions that do not have them integrated, and they are also on the undersides of semi-automatic pistol frames and grips. Their usefulness has led to them being used in paintball, gel blasters and airsoft. See also NATO Accessory Rail Rail System (firearms) Third Arm Weapon Interface System Warsaw Pact rail Zeiss rail References External links Picatinny Rail Specifications Firearm components Mechanical standards Military equipment introduced in the 1990s