Before choosing size 3, check your waist measurement against the LAUMA size chart for this model. Clothing sizes are not reliable for orthopaedic belts because the belt needs to sit firmly around the waist and lumbar area, not simply match your usual trousers or dress size.
Measure the area where the belt will be worn, ideally while standing in a relaxed position. Do not pull the measuring tape so tightly that it compresses the body, and do not leave it loose enough to sag. The goal is a realistic measurement of the waist/lower-back area so the elastic panels can apply even pressure when the Velcro is fastened.
If your measurement is between sizes, consider how you plan to use the belt. A belt that is too small may force you to close the Velcro at the very edge and feel overly tight, especially when sitting. A belt that is too large may not provide enough fixation and may shift during movement. The correct size should allow adjustment in both directions, so you can loosen it for sitting and tighten it moderately for walking or physical tasks.
After receiving the belt, check the fit before using it during heavier activity. It should stay in place, support the lumbar area and allow comfortable breathing. Any numbness, pinching or strong pressure is a sign to adjust the fastening or reconsider the size.