The thermal performance is measured in a rectangular channel (AR = 3:1) with rib turbulators oriented at 45 to the mainstream flow. Ribs are placed on one of the wide walls, while heat transfer coefficients are also measured on a single smooth, narrow wall. The heat transfer enhancement is combined with the frictional losses to evaluate the benefit of turbulator width. Square ribs (w/e = 1) with a rib pitchtoheight (P/e) ratio of 8 serves as the baseline configuration. The rib width, w, is varied while the rib height, e, remains constant. Rib aspect ratios (w/e) of 1, 2, 3, and 4 are considered. In addition, the distance between the ribs is varied to consider the combined effect of rib width and rib spacing. As the width of the ribs is changing, the physical distance between the ribs, l, is varied, and four rib spacings are considered (l/e = 2.6, 6.6 [baseline corresponding to P/e = 8], 10.6, and 14.6). The thermal performance is measured in the 3:1 channel at Reynolds numbers of 10000, 30000, 50000, and 70000. Results indicate increasing the rib width is effective to increase the thermal performance of a cooling passage. However, the rib width and spacing must be varied in conjunction with one another to optimize the thermal performance.