AR15 Sight Options
13. When discussing sights, normally the discussion revolves around iron sights, often called Back Up Iron Sights (BUIS). Although red dot and holographic sights are also available, they are exempt for the discussion of this article. Iron sights for the AR15 are available fixed or flip up styles.
A Front Sight Base (FSB) is one type of fixed front sight.
If using a red-dot or scope you may or may not wish to use BUIS on your AR15. However in a tactical situation it is usually suggested to have the backup sights incase your primary sight becomes non-functional. The general rule of thumb in this case is to run fixed sights as backups if using a red dot or holographic sight, and flip up sights if using a scope.