The O2 Plus air pumps from Pond One are specifically designed for outdoor use and are resistant to the perils the UK weather can throw at them. Fitted with 10m cable, installation is made simple in comparison to other models around. O2 Plus 4000 and 8000 air machines are extremely powerful units. With outputs of 35 and 70 litres per minute these are suitable for seriously large ponds or filters to stimulate aerobic activity or simply to add more oxygen to multiple points around the pond. With the design based upon the Aqua One indoor units these units are fantastically quiet during operation. Outlet size is 1/2″. Each unit comes with a 4, 8 or 10 gang splitter allowing multiple air stones to be run simultaneously.