LAUMA 301 in size 4/XL is intended for larger body frames. With a posture corrector, sizing is especially important because the product relies on elastic tension: if it is too loose, you may not feel the posture cue; if it is too small or over-tightened, it can dig in, irritate the underarm area or make you want to compensate by tensing your neck and shoulders.
A good fit should feel like a gentle reminder rather than a rigid brace. The figure-of-eight construction at the back should draw the shoulders slightly backward and make slouching more noticeable, while still allowing you to breathe normally, sit, stand and move your arms for ordinary tasks. The pressure should be distributed evenly across the shoulder girdle, not concentrated in one narrow point.
After putting it on, check the underarm area first, because this is where discomfort often appears if the straps are placed poorly or the size is wrong. You should not feel numbness, tingling, pinching or sharp pressure. Also check your posture in a mirror: the corrector should encourage an upright upper body, not force the shoulders back so far that your ribs flare or your lower back arches excessively. If comfort improves only when the product is very loose, the size or adjustment may not be suitable for effective use.