If you have a conduit box that has knock out holes that are too big (diameter) for the conduit coupler and pipe you are using, a reducing washer can facilitate adaptation to smaller diameter conduit couplers.
Reducing what with Reducing Washers?
If you have a conduit box that has knock out holes that are too big (diameter) for the conduit coupler and pipe you are using, a reducing washer can facilitate adaptation to smaller diameter conduit couplers.