The AIRWALL Blox is for sealing off the gaps left by the Xpress or Max due to the variability of the spaces you work in. It is designed with a mind towards simplicity. It has has two vent carriers but no clips or snaps. It can be used one at a time or daisy chained together but is dependent on an Xpress or Max for its air supply. It is often the exact thing you need when you're not getting the seal you're looking for.