Air volume spacers are a fast and easy way of tuning your suspension. Changing the quantity of Air Volume Spacers changes the air spring curves to be more(adding spacers) or less(removing spacers) progressive through the mid-stroke and bottom-out resistance
If your sag is set properly on your bike but you're either using too much travel, or you would like a bit more support through your mid-stroke, volume spacers are a great way to customize the performance of your bike.