the outer shell is too tight, almost tighter than the inner part. Do not choose your regular size but 2 or 3 sizes larger. the sizes are for shrimpy soprano choir boys waiting for their chestnuts to arrive.
European Size Medium apparantly equals Chinese Size Extra Large, I just found out. Despite Alsoto's claim that they would be equal sizes. Normally size M suits me fine, for safety I chose L, still too small. I do not want my voice to become a soprano voice. So, how do I exchange size L for a size XL?