adjustable - yet small

Husband and I both tried and our shoulders/upper back was just too large.  17-year-old son is - 170lbs and has a narrow upper body.  It fits him well.  He has been wearing it for an hour a day during weight lifting and he loves it saying it has added benefits in the gym. Correct posture gives the body better-left strength and stamina.  Then I see him hunched over his gaming keyboard and will suggest he wear it a bit in the evening to sit him upright. I only wish they made them for bigger sizes too. I have no experience with other brands so I can not compare style or materials.