Spherically Mounted Rertroreflectors (“SMRs”) are precision tools used in a variety of environments to measure and record data on tools, assemblies, and other objects using a laser tracker. SMRs can accumulate dirt, grime, and other foreign material which can reduce the SMR’s ability to return the laser beam and track well. It is suggested you clean the optic if necessary but only when necessary. SMRs are an important part of your laser tracker measurement system and should be well taken care of. SMRs are precision parts that do require occasional cleaning.