12-10 gauge heavy duty nylon-insulated butt splice terminals. Seamless construction.
A more robust terminal connects two wires with two crimps on each end.
The nylon insulation provides greater durability. It also allows you to see the wires in the splice to ensure a proper crimp.
Requires four crimps. Each end requires a terminal to wire strands crimp and terminal to insulation of wire crimp. Standard tools perform both crimps. For heavier usage, use a tool that performs both crimps at the same time.