Craftsman & Ridgid Replacement Filter Cap & Wingnut This cap is not compatible with Ridgid filters, this only allows Kopach filters to fit onto Ridgid vacuums Required one time purchase for Ridgid Users to make up the 1/2" difference between OEM filter and Kopach filter Reversible cap allows for assembly of filters to Craftsman and Ridgid shop vacs Wingnut secures the cap onto the filter