A barbell is one of the most common types of fitness equipment that can be found in almost any gym. ... It is used for all forms of resistance training exercise including bodybuilding, olympic weightlifting, and powerlifting. A barbell is essentially a long bar that is normally 6-7 feet in length. Plate sleeves are at both ends of the barbell so that weight plates can be added to increase the level of resistance that is applied during an exercise. The diameter of the bar itself can vary drastically between 25 mm to 50 mm in diameter. Barbell collars or clips can also be used to prevent the weight plates from sliding up and down the barbell sleeves during an exercise. Barbells commonly weigh either 20kg or 15kg and they also come equipped with a rough texture called the knurling. The knurling ensures that the barbell user has a strong and sustainable grip throughout each exercise.