The circular dial in the top middle of your picture adjusts the tension. Some of these require you to push it in to allow movement, others just need more force to turn. Once you have the helmet on your head you reach back and twist the dial FCE one direction to loosen and the other to tighten. It is the same as a welding mask and I prefer to actually hold the helmet very slightly off my head in the middle so it floats using the headband, allowing more air flow. It is much cooler and also the weight is more even around your head rather than rubbing in one place the whole time.