The fan speed balancer is also available as an add-on if you have two fans that are not ideally suited to be used together. For example, if you are using two fans that are the same in terms of air movement you will want to give more power to the outlet as the filter attached to the outlet will reduce its flow. The Fan Balancer will enable you to create a small amount of negative pressure in your grow space so all of the air coming from your grow room will be passed through your filer, ensuring there are no unwanted odors escaping whilst not putting too much strain on either of your inlet or outlet fans.