Step-Down Butt Connectors, Vinyl Insulated Term.

The Step-Down Butt Connectors have 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.