Metric flangeless fittings offer the same benefits as flangeless fittings with the additional feature of being used for metric tubing and ports. They are specifically designed to connect 1,8, 2,0, 2,5, 3,0, or 4,0 mm Ext.Ø tubing to flat-bottom ports when paired with the appropriate M6, 1/4-28, or 5/16-24 flangeless nuts.