the 18.5 inch has a fixed cylinder choke and the 28 inch as multi choke with a modified choke tube suppliedUPC: 049533310149
Description: MAV M88CMBO 12M/28MC & 18CB
Brand: Maverick Arms
Model: Model 88 Field / Security Combo
Type: Shotgun: Pump Action
Caliber: 12 Gauge
Finish: Blue
Action: Pump Action
Stock: Synthetic Black
Sight: 18.5 Bead and 28 Twin Bead
Barrel Length: 18.5 and 28 Vent Rib
Overall Length: 38 & 47.5
Weight: 6.25 & 7 lbs
Capacity: 5+1
Safety: Cross-Bolt Safety
Receiver: Black
Chamber: 3
Chokes: Multi-Choke (Modified)
Butt Plate: Black Rubber Recoil Pad
Features: Vent Rib, Dual Extractors & Twin Action Slide Bars

Dallas the 18.5" Cylinder Smooth Bore Security Barrel has a "Fixed Cylinder Choke". The 28" Field Barrel comes with a AccuChoke Modified Choke Tube. *****Note the Field Barrel can take any AccuChoke as they or removable/screw-in*****

The 19 inch barrel has a cylinder bore choke and the 28 inch barrel has a modified choke. Hope this helps.