Pressurised meaning you can have this filter above the level of the water you are filtering. UV pond filter for ponds up 4500 litres does not include the pump Best pond filter on the market today. This filter is made by Sunsun who are the largest manufacturer of of aquarium and pond filters in the world. This is the smallest filter of a series of three sizes. This filter is packed with useful features making this range of filters the most technically advanced pond filters on the market today. The pump power is 4500 litres per hour. The filter has an indicator to show you when it needs a clean. It also has a an out flow volume indicator so you can see at a glance how well your out flow is working. This filter can take varying diameter hoses from 20 to 35 mm. (hoses not supplied). The filter is pressurised and will operate up to 1 metre above the pond level which is handy if you have a waterfall or fountain. The filter is supplied with sponge media, so no need to purchase any media. Also supplied is a clear instruction manual written in English with easy to understand instructions. This filter is very easy to use and clean and is the best pond filter I have ever seen and I have sold thousands of filters over the years. quick dispatch. questions welcome.