The unit is specified with Worm Hole Climb-Through Compartments - it comes with a MDF & Twist Pile insert to place over the Worm Hole Shelf to turn it into a Full Shelf.
Ballast needs to be added to the unit to make it Freestanding - we recommended filling the chamber with at least 40kg of sand for a single cat household.
For more information please visit our SixToo™ page.