Just like the original JEBS High Voltage choke tube design, the Black Nitride waterfowl choke tubes are held to the same quality and durable standards as before. Besides looking incredible in the black, there are many additional benefits to the Black Nitride process: provides additional lubrication, protects against corrosion, wear resistant, and 82 on the Rockwell Chart.Choke Tube Comparisons for JEBS Restrictions Versus Standard Factory Choke Sizes:.575 - Similar To A XX-FULL .580 - Similar To A X-FULL .585 - Similar To A FULL.590 - Similar To A MODIFIEDCR - Similar To A IMPROVED (Shots 20 yards and closer)