The M8-45B is a white steel zinc bolt that is needed to assemble brackets. (x4) bolts are used to fix 6-inch casters to Flexpipe structures. This part cannot be used for anything but the assembly of the four inch brackets. To create a bracket set, you need to connect two WF-LARGE brackets with two M8-45B and two M8-N nuts. (you will need two sets for every caster). This has been improved over the years to be easier to install on Flexpipe structures, however, be sure to check the installation steps for the W-6PSB, W-6PF casters to see how to use the M8-45B.