One of the principal advantages of the OTKB(/M) optical tweezers system over a black box system is the ease with which the design of the optical trap can be modified to add functionality. For example, the OTKBFM and OTKBFM-CAL can be easily attached to the base OTKB kit, and provide the user with the components needed to add trapping force, stiffness, and position measurement capabilities to the OTKB optical trap. The OTKB-FL and OTKB-FLS are modules that add fluorescence microscopy capabilities to the optical trap. More details on these modules are on the System tab as well as below.