Posture Medic's is designed to help promote proper posture. Most users will find that the Original Strength provides an excellent workout and stretch for their shoulder/chest area. This non-bulky multi-purpose exercise tool is an excellent accessory to have pre, during, and post workouts. The Posture Medic Plus Strength is designed for users who are more active. The Plus Strength utilizes a proportionally heavier resistance band compared to the Original. Size Guideline OC-2300-1 Plus Strength Purple Small OC-2300-2 Plus Strength Blue Medium OC-2300-3 Plus Strength Silver Large OC-2300-4 Plus Strength Orange X-Large OC-2300-XS Original Strength Light Blue X-Small OC-2300-S Original Strength Red Small OC-2300-M Original Strength Green Medium OC-2300-L Original Strength Yellow Large OC-2300-XL Original Strength Black X-Large How to Measure Measurement is based on your height and weight Posture Medic Uses - Office jobs- During a workout- To help promote proper posture Size Chart