The easiest solution to connect your welding hose to your concentrator is to use a plastic "christmas tree connector". They can be found wherever concentrator accessories are sold. These have barbs of increasing size on one end (to fit into your clear hose coming out of the concentrator) and a size B female fitting on the other. To connect this plastic piece to your hose you will need a brass male B to B fitting. Welding supply houses also carry brass barb fittings. They usually come in 2 pieces, a barb and a female nut. This way you can select both the size of the barb and the size of the nut that fit together. Just like using the christmas tree connector you will also need a male B/B connector to connect the barb/nut to your hose.