The Bodylastics Snap Guard cord was introduced into all of the bands in 2011-2012.
You cannot see or feel the cord when looking at or squeezing the resistance band.
To tell if your bands have the Snap Guard cord, take one of the bands and fold the clip webbing aside so you can look down the end of the tube. Take a flash light or bright light and look down the end of the tube and you should see a black stopper ball with the end of the white cord about an inch down inside the tube. This is the end of the Snap Guard cord. If you do not see this ball and white cord, then your bands do not have the anti-snap cord inside them.