Jebs Choke Tubes 20 Gauge Benelli/Beretta Mobl High Voltage .585 Modified/Improved Waterfowl Choke Tube Black Nitride JPCBN - 20F2/585. The patented design gives the shooter a more consistent shot pattern a more distinctive and shortened shot-stream and incredible knock-down power for those much needed ''longer shots''. Choke Tubes are offered in Ported as well as Non-Ported models. Specifications for Jebs Choke Tubes Black Nitride High Voltage Waterfowl Choke - 20 Gauge: Manufacturer: Jebs Choke Tubes Finish: Black Nitride Fabric/Material: 17-4 Heat Treated Stainless Steel Gauge: 20 Features of Jebs Choke Tubes Black Nitride High Voltage Waterfowl Choke - 20 Gauge All tubes are made from 17-4 Stainless and heat treated to 44 Rockwell hardness to accommodate any type of shot SteelTungstunHevi-ShotLead or anything the shooter wants to shoot Package Contents: Jebs Choke Tubes Black Nitride High Voltage Waterfowl Choke - 20 Gauge Jebs Choke Tubes JPCBN - 20F2/585: 20 Gauge Benelli/Beretta Mobl High Voltage .585 Modified/Improved Waterfowl Choke Tube Black Nitride