The Mini Pro Series Side Barriers are specifically designed for use with The Net Return Pro Series Mini Net. The Side Barriers insure that mishit balls never leave the hitting area.
If using the Mini Pro Series net indoors or in an area where errant balls are a safety concern, the Side Barriers are required. Many golfers also choose to add the Side Barriers when considering "Friends and Family" hitting into the net.
If you are an accomplished golfer or using the Mini outdoors where safety is not a concern, the Side Barriers are not required.
Understand also that the Mini Side Barriers can be added at anytime and are not required for use with the Mini Pro Series net.