Low Profile Compact Design Allows Easy Access to Hard-To-Reach DEF, Breather Line, Coolant Line, and Fuel Line Connectors Found on Most Cars, Truck and Heavy-Duty Vehicles. Low profile compact design allows easy access to hard-toreach DEF, breather line, coolant line, and fuel line connectors found on most cars, truck and heavy-duty vehicles. 1/4" square drive allows use with a breaker bar or extension to reach into tight spaces. Kit comes with six sizes. Four sizes are used to compress connectors and two are used to spread connectors to remove the line.