Muscle Mapping engineered knitted technology was developed especially for the law enforcement professional. This garment, made of 88 percent Tactel nylon, 7 percent nylon and 5 percent Lycra spandex, has three compression zones: highest compression in mid-section, medium compression on chest and moderate compression under the arms. These zones virtually add muscle tone throughout the torso and offer a support system to muscles and back. Mesh fabric under the arms and seamless side seams reduce friction and increase breathability. Dri-X-treme wicking enables quick drying and increased comfort. The 5.11 Tactical shirt is designed to work in conjunction with body armor with a snug, more effective fit.