The arms and rear are built-in 4-way extend material and so are highly breathable, outstanding for fabric on which water just beads off. Once again not waterproof, but good plenty of to lose a light shower though remaining supremely breathable. The only concern we had was with the in shape. https://wind-proof-jacket24571.full-design.com/the-5-second-trick-for-wind-jacket-black-73892281