Tricep cable pushdowns are an excellent isolation movement that lets you focus on upper arm and triceps for maximum growth and stimulation.
Load up a high pulley machine with weights and a bar attachment.
Keeping back straight, incline forward a bit and bring your upper arm perpendicular to the floor. Keep the forearms towards the machine to ensure you isolate the triceps during the movement.
Slowly brings the bar down till it reaches your thighs.
After a pause, slowly bring the weights back up to the start position.
Once completing your set, re-rack the equipment as needed.
You can also use the rope extension to even further reduce the usage of forearms and isolate triceps