Metric tube nozzles have a stop on the inside that forms an airtight seal when the tube is fully inserted into the nozzle. Metric tube nozzles are designed to match metric tubing, and are similarly based on outside diameter (OD) x wall thickness. Metric tube nozzle designations utilize the largest wall thickness for the given OD, but fit all smaller wall thicknesses as well. Metric tube nozzles are grey in color. Tubing nozzles for nominal inch sizes are also available