Embodiments of the present invention generally relates to apparatus for use in film depositions. The apparatus generally include pre-heat rings adapted to be positioned in a processing chamber. In one embodiment, a pre-heat ring includes a ring having an inner edge and an outer edge. The outer edge has a constant radius. The inner edge is oblong-shaped and may have a first portion having a constant radius measured from a center of a circle defined by an outer circumference of the ring. A second portion may have a constant radius measured from a location other than the center of the outer circumference. In another embodiment, a processing chamber includes a pre-heat ring positioned around the periphery of a substrate support. The pre-heat ring includes an inner edge having a first portion, a second portion, and one or more linear portions positioned between the first portion and the second portion.