In this 21st century there are not many roof vents that achieve the manufacturers claims.
The two outstanding achievements for roof ventilation are a cooler home in summer and for a drier roofspace from condensation complications during winter.
Most turbine vents do nothing but swing around till the bearings collapse, whilst they are supposedly reliant on ceiling vents or eaves vents. However, most turbine vents that have been installed have no inlet air at all, no ceiling vents or eaves vents.
The real trick to effective roof cavity ventilation is to have a balanced system of two opposing vents of the same volume. So how can any type of roof vents for houses work effectively using eaves or ceiling vents for inlet air when the roof vent is not equal to the eaves or ceiling vent or has no inlet air at all. This is the case with most roof vents for houses.
Smoothline vents and Universal Tile Ventilators are balanced systems of the same volume and allow ambient air to circulate the roof cavity removing heat in summer and alleviating condensation in winter.