About 18 in length.
Thoracic spine extension foam roller.
Rolling back and forth horizontally relaxing with it lengthwise along their spine to open the chest or even some typical extensions mid thoracic.
These mobilizations will improve the ability for you to extend and rotate through your thoracic spine taking load off of the lower back muscles and spine.
How to do the thoracic spine extension this exercise will help stretch out the chest and back muscles relieve muscular tension and maintain thoracic mobility.
This extra dense foam stretches spinal muscles and mobilizes the spine during warm up exercises prior to treatment.
Thankfully thoracic mobility can be easily maintained and improved using a foam roller and the thoracic spine extension exercise as described below.
Kudos to them they took some initial to work on their mobility.
How to do it.
I personally would have no problem with a patient telling me that they use a foam roller on their thoracic spine.