Within your body, your fascial system is in a constant state of remodelling and change as we saw in the video "Fascia 25x" (Have another watch here if you've forgotten). This is especially true in your ribcage and thoracic spine.
Limited range of motion through the upper back can impact your breathing, flexibility in all directions, core stability, the range of motion in your shoulders and can cause increased loading into the lower back. These thoracic mobilisers help gently mobilise this area to keep it working optimally and performing at top capacity, without pushing into any painful restrictions.
Oscillate gently in and out of each direction, tractioning and releasing the tissues for optimal hydration. You may find that there are some directions where you have a large range of motion but in other directions, you'll be tighter than you thought.