When you are fitting cooling hoses to a filter you need to make sure that you get the correct diameters of flange to enable them to fit securely. Designed to fit the OptiClimate 3500 and 6000 air conditioning units, the Flow Filter Flange 250-200mm gives you the right dimensions for fixing. The flanges come with screw holes, enabling you to attach them to the appropriate surface. The hose connection is tapered and is easy to install. The diameter of this flange is specifically for the OptiClimate 3500 and 6000 units so make sure you get the right size. The first number, 250mm, gives the filter diameter the flange can be attached, and the second number gives the connection diameter to ensure the precise sized hose can be joined to the unit. You'll save yourself time and hassle by checking that you are ordering the correct size.