The outside diameter of the butt connector is the same on both ends and only the inside diameter is adjusted for the different wire gauge. This means that the side for the smaller wire has a much thicker wall than normal and is extremely difficult to crimp. Almost impossible to crimp properly & wire can easily pull out!!

We vary the inside AND the outside diameter of the connector which means that both sides will make a sound mechanical crimp. Also, has a window which allows for visual inspection. Easy to crimp & provides strong crimp termination!

Has a color stripe to indicate where the smaller size of wire is inserted. However, it must be crimped in the larger crimp die. For example, on their connector for
14-16 to 10-12 AWG, the BLUE stripe indicates the side where a 14-16 AWG wire is to be inserted. However, it must be crimped in the YELLOW crimp die.
CONFUSING!

Has two stripes - one on each end - to indicate which wire size to insert. Plus, the stripe matches the crimp die that needs to be used. For example, the blue stripe indicates the side where a 14 AWG or 16 AWG wire is to be inserted, and it will be crimped in the blue crimp die.
MAKES SENSE!