Briley Browning Invector Plus Helix Choke 12 Gauge Modified .020. This constriction increases velocity and energy transfer resulting in the projectile traveling a shorter distance per shot. The Octagonal shape defies cross sectional area changes that can occur between flush mount chokes and choke tubes with a longer parallel section. This reduces the possibility of the fouling that can occur when the choke tube is cold. The Octagonal shape also allows for easy choke tube removal while guaranteeing concentricity with the bore. Specifications for Briley Browning Invector Plus Helix Choke Tube: Manufacturer: Briley Gauge: 12 Choke Tube System: Browning Invector Plus (+) Gun Make: Browning Package Contents: Briley Browning Invector Plus Helix Choke Tube Briley INPH12M: Browning Invector Plus Helix Choke 12 Gauge Modified .020