FNH Otis Cleaning Kit 5.7x28MM. A clean gun is an accurate and reliable gun. Make sure your FN firearm gets cleaned right every time with a genuine FNH USA cleaning kit. Easy to use, easy to carry and easy to store, FNH USA cleaning kits are a must-have accessory for every FN firearm. For use with all FN products chambered in 5.7x28mm.