> That is even more odd. Maybe the sizes are so close they just write them in > American measurements to sell here. All the sites I have found use English > measurements. 12mm metric barbs will take 1/2" tubing with out a problem. Same with 16mm and 5/8th. Solution is a 1/2" to 5/8" step-up barb and a couple of hose clamps. However that does mean you will need to change anything down-stream of the heater to 5/8" or 16mm. Dana Rasmussen Seattle _______________________________________________ GSAS-Member mailing list GSAS-Member@thekrib.com http://lists.thekrib.com/mailman/listinfo/gsas-member