The best type of bar to use on a preacher arm curl bench is the EZ curl bar, often referred to as the arm curl bar. Due to its zig-zag shape, it offers a large variety of hand grip positions, which helps reduce strain on your arms, particularly the wrists, elbows, and shoulders. Alternatively, you can use a standard barbell or dumbbell as well. However, research has shown that the EZ bar outperforms the straight bar and dumbbells when it comes to activating the biceps brachii and brachioradialis.