Omnifilter Ow30-s6-s06 Water Filter Tank Wrench Water filter accessories whole house/undersink housing wrench For use with Omni under-sink water filter numbers CBF20, SFM2, UC2. CBF1, CBF3, OT32, OB3, and RO2000 Inside diameter of wrench is 4.36&rdquo; to 4.32&rdquo; Carded