Size Regular (16 -18 ) The Theratrac Gently Stretches Neck Muscles Allowing The Vertebral Discs To Realign Freeing The Nerve Root Tissue From The Pressure Of The Discs The Theratrac Helps Locked Neck Muscles To Slowly Stretch And Relax Allowing Misaligned Vertebrae To Resume Their Normal Supportive Position The Theratrac Cradles The Head And Neck Via A Curvature In The Neck Portion Of The Device As Well As A Special Head Rest Section That Is Vertically Pneumatic 5 Year Limited Warranty Both The Headrest And Neck Region Inflate With Over 30 Lbs Of Adjustable Pneumatic Pressure To Create Traction In The Cervical Curve