These EasyPro pump vaults are round in design to provide superior structural support. Great for building disappearing pondless waterfalls or used for creating bog filters on lager ponds. The pump vaults have slots cut into the ribs of the unit to allow water to flow into the unit protecting the pump from medium to large debris. A 12" extension is available for the smaller pump vault to allow you to create deeper reservoirs for your pondless basins or bog filters. Versatile and strong these units are great for the do it yourself home owner or the professional contractor.