Barbell bars are not universally 20kg. While it is common for a standard Olympic barbell to weigh around 20kg, there are various types of barbells with different weights suitable for different purposes and levels of fitness. For example, training bars, which are lighter and designed for beginners or those working on technique, often weigh less than 20kg. Similarly, specialized bars for exercises like powerlifting or Olympic lifting may have varying weights and specifications to accommodate the specific needs of those disciplines.