1.5" TC x QCOut of all the ways to attach silicone tubing (sold HERE) to your brew kettle or conical we like quick connect ball lock fittings the most. The ease of connecting disconnecting and cleaning is unmatched by standard hose barbs or cam locks. These fittings can easily be attached using one hand even with heavy brewing gloves. The inside diameter of our QC fitting is 1 2". This creates a full port design and will not restrict flow going through the barb.