Embodiments of the disclosure generally relate to a support cylinder used in a thermal process chamber. In one embodiment, the support cylinder includes a hollow cylindrical body comprising an inner peripheral surface, an outer peripheral surface parallel to the inner peripheral surface, wherein the inner peripheral surface and the outer peripheral surface extend along a direction parallel to a longitudinal axis of the support cylinder, and a lateral portion extending radially from the outer peripheral surface to the inner peripheral surface, wherein the lateral portion comprises a first end having a first beveled portion, a first rounded portion, and a first planar portion connecting the first beveled portion and the first rounded portion, and a second end opposing the first end, the second end having a second beveled portion, a second rounded portion, and a second planar portion connecting the second beveled portion and the second rounded portion.