Lower segment rotates enabling exact alignment of system. Systems should be vertical as far as possible for most efficient evacuation and should not exceed 45° from the vertical, otherwise resistance to flue gas flow will result. Bends should be kept to a minimum and a vertical rise of 600mm minimum should be allowed for immediately above the appliance. As a general rule, the vertical distance between the appliance and the flue terminal should always be at least twice the horizontal distance between the appliance and the terminal The K Vent range includes 30° and 45° fixed bends which can be used where the flue system needs to be offset e.g. to avoid trusses and terminate to a ridge terminal.