Meprolight Tru-Dot sights are up to 20% brighter than other tritium sights. The front dot is slightly brighter than the rear sight to help the shooter focus on the target. Light tubes are sealed with a patented bonding process that makes them impervious to solvents and oils. Tru-Dot sights have a 10-year illumination warranty. Meprolight Sight Sig Sauer P220, P225, P226 and P228 adjustable sight has its own Tritium gas light source (no batteries and no charging required), is not affected by weather or gun solvents. May require fitting on some models. Made of blued steel with tritium inserts. Fits guns originally fitted with adjustable factory sights. 10 year illumination warranty.