Stand in between a cable crossover stand and set the cables just above head height. Keep a slight bend in your knees and grip the cables with your palms facing up and arms fully extended.
Make sure you're standing directly in the middle of the stand, and then curl the cables toward the sides of your head as if you were hitting a front double bicep pose.
Continue until you feel a full contraction in your biceps, pause briefly, and then return back to the starting position.