The demand for faster operation, higher quality output and increased efficiency in automation and machine control systems has led to increased demands on guidance systems. Innovation of re-circulating, linear bearing guide technology has launched that option as the preferred choice for most precision linear motion stages. As the use of re-circulating linear guides increases, many vendors have entered the market, producing nearly identical products. All vendors promote similar load capabilities, running speeds and accuracies. A machine designer has difficulty in selecting a specific brand. An extensive study was conducted to evaluate the running accuracy of several commercially available, re-circulating bearings and configurations. This paper will describe the results of the study and explain the reasons for various inaccuracies. These results will help understand the subtle details of the different styles.