Iron sand fills the panels rather than loose plates, spreading 6 pounds evenly across the chest and back so the load sits close to the torso and does not swing during a run. Six pounds is a starting load, enough to raise the demand of walking, jogging and body weight circuits without altering running form the way a heavy vest can. The neoprene shell measures 14.2 by 12.0 by 2.8 inches, hugging the body closely to prevent the chafing that comes from a vest riding up between strides. An adjustable buckle sets the fit across different chest sizes and layers, and it releases quickly at the end of a session. A reflective stripe across the shell picks up headlights during early morning and evening training. Small pockets hold a key or a card. Spot clean with mild soap and air dry away from direct heat.