APEC Water ULTIMATE Series CT-1SED is for RO-CTOP Stage 1, RO-CTOP-PH Stage1, and compatible with all 10 inch industry standard sized countertop water filter system pre-filter set is USA made with 1/4" quick connect fittings for easy replacements 1st stage sediment filter to remove dust, particles, and rust Friction-welded construction provides a reliable, no-leak seal Compitable with Omnipure K2505JJ