Cycling jerseys are designed to improve aerodynamics and absorb perspiration. Most jerseys are made from tightly woven synthetic materials, such as Polyester and Polyester-Lycra blends that conform to your upper body, shoulders and arms. The inner lining has a larger weave that wicks moisture away from your body. Jerseys are available in standard sizes and extra large sizes and you have the option of long sleeves or short, pullover, full zipper or partial zipper styles. The correct fit ensures maximum performance and comfort of your cycling jersey.Stand erect and extend your arms as if holding the handlebar grips on your bicycle. This flexes your pectoral and shoulder muscles. Ask the salesperson to measure the circumference of your chest with a seamless metric measuring tape to establish the size of the jersey.Measure the distance from the base of your neck to your groin to establish the length of the jersey. The jersey must be long enough to fit over and below the waist of your cycling shorts for optimum aerodynamics.Try on a sample jersey that's provided by the retailer. Extend your arms ahead as you lean forward at the waist to simulate riding your bicycle. Reach behind to make sure you can access the back pockets on the jersey.Discuss the fit and comfort with the salesperson. If necessary, try on another sample jersey in a size larger or smaller to establish the optimum fit and comfort before purchasing your cycling jersey.