A device is insertable into a conduit, such as a pipe, for guiding fluid flow of a material. The device includes a tubular member having an inlet and an outlet and defining a cylindrical fluid path there between, enabling fluid to flow through the device. In order to improve fluid flow, the internal surface or wall of the tubular member includes one or more helical profiled portions which extend radially inwardly towards the axis of the tubular member. The helical profile portions can have from 180° to 900° turns along the length of the portion. In certain embodiments two parallel, identical helices, axially offset from one another can be included.