The attractive prospect of CW AlGaAs/GaAs monolithic linear diode laser arrays (aka bar arrays) arises from the continuing improvement of the attributes of pulsed diode lasers, such as external quantum efficiency, lifetime, and coherence capabilities. Unfortunately, for close packed arrays, CW operation of an array at ambient temperature is limited to a few watts of optical power. Wafer thin coolers (on the order of lmm thick) that have been designed to remove heat fluxes of over 100W/cm2 from laser array packages (a diode bar soldered directly to the coolers via a 'sandwich' package) which operate more effectively in a CW mode. Tests were conducted to compare the thermal and optical performance of five types of such wafer thin coolers; a double pass microchannel cooler, two types of single pass microchannel coolers, and two versions of a compact high intensity cooler (CHIC). Thermal tests were conducted on the coolers alone at heat fluxes from 5 to 125W/cm2. CW power vs. current (P-I), uniformity of emission, and wavelength vs. current measurements were made for each cooler/bar package. The optical experiments were conducted at 5 and 15kg/hr flow rates, and at 15° and 25°C inlet temperatures, using water as the cooling fluid. Results of the optical tests performed on 0.9cm linear arrays mounted on the wafer thin coolers showed impressive performance, such as 19.4W CW at 30 amps input current, and a very small wavelength spread across a bar. Such performance levels warrant these cooler/bar packages as a standard in CW bar operation.