Jebs Choke Tubes High Voltage Choke Tube Features Just like the original JEBS High Voltage choke tube design our 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. Jebs Choke Tubes High Voltage Choke Tube Specifications Brand: Jeb s Choke Tubes Model: High Voltage Choke Tube 20GA Invector Plus .575 Finish: Matte