MRS Sigma miniature linear guides by PCB Linear, Rockford, Ill., have sigma-shaped, ceramic-coated aluminum alloy rails that are available to 5 m and die-cast streamlined carriages that provide a cost-effective alternative to conventional ball and roller linear guides and bearings.  Self-lubricating, sigma-shaped polymer inserts eliminate a need for seals and wipers. The flat bottomed rail and a keyed carriage—available in three colors—help make installation simple while the sigma shape improves accuracy and prevents carriage/rail drift, thus providing extra stability.