Seated Biceps Curl / Triceps Press.

Arm day, one seat.

The arm pad and handles switch over, so the same station runs both curls and triceps presses without you getting up. The upper arm sits fixed both ways, no arch, no momentum, no help from the shoulders when it starts to burn. A 60 kg stack in 5 kg steps is plenty when the joints are locked and the muscle actually has to do the job alone. You change exercise. Not place.