Unfortunately, this filter has been discontinued by the manufacturer. There are no replacement filters available.
You can purchase a new faucet filter system:
Faucet water filters and Culligan faucet mount water filter systems
Or, if you don't want a system connected to your faucet, you could consider an under sink system such as the Culligan US-EZ-4 system:
Culligan US-EZ-4 UnderSink Drinking Water Filter and Culligan USEZ4 Under Sink Filter 01019054.
Thank you,
WaterFilters.NET