I received the Big Dot Sights and installed them on my M&P 40 Cal Shield. Rear Sight installed without any work and the Front Sight required some minor fitting. I didn't lock tight the rear until i shoot the pistol to make sure my carry load is centered windage wise . Can't shoot at the moment , because it is pouring down rain. Both front and rear original sights were Red Locktited in and had to transfer some heat to both to get them to move, they dam sure wouldn't have came out on there own. I believe the new Big Dot Nights will be great on a conceal carry gun like my Shield and will post how well i like them once i shoot the pistol.