There seems to be quite a few dissatisfied CPP customers on here. I suspect they supplied hoses with the wrong side fittings, or someone left the insert part of the fitting(s) out when they rebuilt the box. Look inside the fitting on the box, there should be a brass nipple in there. You need a 16mm reverse flare fitting for the pressure side and a non-standard 17 mm fitting for the return side at the box. Usually the pump end fittings on both lines are 16mm. If you try to put a 16mm fitting in the return port, it will seem to fit loosely, but will leak like a screen door. Don't use any type sealant or sealing tape on the fittings.