Jebs Choke Tubes High-Voltage Waterfowl 20 Gauge Choke Tube Retay Masai Mara .580 Choke Restriction Black Nitride. The patented design gives the shooter a more consistent shot pattern a more distinctive & 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 High-Voltage Waterfowl 20 Gauge Choke Tube: Manufacturer: Jebs Choke Tubes Fabric/Material: 17-4 Heat Treated Stainless Steel Gauge: 20 Quantity: 1 Condition: New Package Contents: Jebs Choke Tubes High-Voltage Waterfowl 20 Gauge Choke Tube Jebs Choke Tubes JPCBN-20J2/580: High-Voltage Waterfowl 20 Gauge Choke Tube Retay Masai Mara .580 Choke Restriction Black Nitride