Cliff Keen Ultra Mesh Side Panel Basketball Referee Shirt. The shirt of choice for collegiate-level officials and approved for NFHS contests. Our premier MXS® ULTRA-Mesh® fabric is knit from the finest blends of natural, performance yarns. Features a 2” longer split tail, double stitching and convenient lanyard loop. Shrink, wrinkle and stain resistant. our side-panel shirts are fortified with our MXS® fabric technology, wicking moisture from the body to provide you the with a performance edge in the latest officiating style!