the men's and women's bars: the men's has knurling in the center but the women's does not. The Olympic barbells used in competition are certified by the IWF. Bumper plates The weight plates, typically referred to as "bumper plates" because of their rubber coated design, weigh between 10 kg and 25 kg in 5 kg increments. The bumper plates are coated with rubber to allow the weights to be dropped from various heights—either after a successful lift or during an unsuccessful one. Olympic bumper plates conform to international standards for coloring. That is, 10 kg is green, 15 kg is yellow, 20 kg is blue, and 25 kg is red. Competition iron plates In addition to the rubber bumpers, smaller competition iron plates can be used to add weight in small increments to the bar. The color designations for these iron plates are as follows: 1 kg is green, 1.5 kg is yellow, 2 kg is blue, 2.5 kg is red, 5 kg and 0.5 kg are white. It is useful to note the color assignment of these iron plates is consistent with the heavier bumper plates (i.e. 1 kg and 10 kg are green, 1.5 kg and 15 kg are yellow, etc.). Collars Weight plates are secured to the bar using collars on each sleeve that weigh exactly 2.5 kg each. Singlet Lifters typically wear a one-piece close-fitting leotard often called a singlet. The wearing of a T-shirt underneath the singlet is optional. Belt A weightlifting belt of 120 mm maximum width may also be worn to increase intra-abdominal pressure. Chalk Chalk is regularly used by Olympic lifters, generally prior to each attempt at a lift. Lifters rub their hands with the chalk to promote dryness and prevent the bar moving in their hands. Tape Olympic lifters frequently use tape to cover the areas of their bodies exposed to friction while completing Olympic lifts. Tape is most commonly found on the Olympic lifter's thumb. A taped thumb not only lessens the risk of calluses, but it also reduces the pain associated with the hook grip. Olympic lifters also tape their wrists, preventing exaggerated and uncomfortable joint movement during lifts. For particularly heavy overhead lifts, a taped wrist enables the lifter to regulate wrist extension and delimit the translation of the radius and ulna distal heads. However, while taped wrists can prevent wrist and forearm injuries in the short-term, excessive