Folding Chair with Back Angle Adjustment Structure

A chair comprising a backrest assembly, a foot tube assembly, and an armrest assembly, the armrest assembly comprising an armrest slidably connected with an armrest base, the armrest base being operatively connected to an upper portion of the foot tube assembly, a back end of the armrest being operatively hingedly connected to the backrest assembly, the armrest assembly further comprising an elastic member operatively connected to the armrest and the armrest base, the elastic member extending in a direction of sliding of the armrest relative to the armrest base, the armrest assembly further comprising a lock, the lock being moveable between an engagement position wherein the armrest is fixed to the armrest base and a disengagement position wherein the armrest is slidable relative to the armrest base under bias from the elastic member.