This is an F Type crimp die I can use for F / B type crimps of larger wire. It is used for D-Sub / F Type / B Type terminals. This die is for 14GA to 10GA but is shows the "butt cheeks" better than my die for 22-26GA does. On the top of the die just below the 14, 12, 10 is the little "dimple" that looks like butt cheeks. It is what "folds and rolls" a D-Sub style terminal over giving it a "double D" type profile.
This die is actually a double D-Sub which simultaneously rolls and forms the strain relief and crimps the bare wire.
Note: AMP and Molex interchangeably call this type of tool an F Type or B Type crimp. These terminals are not F or B type but this type of crimp tool works extremely well for this small gauge wire..