A red dot on and for what? There are many out that aren't even good paperweights. The scope that will work fine on a rimfire or smaller pistol caliber would be broken quickly by a centerfire rifle, magnum pistol or shotgun. About the best I've come across that is just about a universal fit is Millett SP series red dot. They have 1" or 30mm bodies, a range of dot sizes and I haven't been able to break one yet. Even using a M1a which is known for being HARD on scopes. Price isn't bad either being right around $100 new. You can find them for much less used and I would call them a very safe buy as used stuff goes.