Hi Drea and welcome. It is threaded for chokes and Includes:
Magazine Plug
Choke Tube Wrench
3 Flush RemChoke Tubes (Improved Cylinder, Modified, Full)
Cheers, stay safe and enjoy!

it has screw in Rem chokes and includes 3 Flush RemChoke Tubes (Improved Cylinder, Modified, Full)
see *****
Remington 870 Fieldmaster Synthetic Specifications and Features:
Remington Item Number: R68872
Pump Action Shotgun
12 Gauge
4 Round Capacity
26" Vent Rib Barrel
3" Chamber (also accepts 2-3/4" Shells)
Accepts RemChoke Pattern Choke Tubes
Bead Front Sight
Improved Twin Action Bars
Milled Steel Receiver
Receiver Drilled/Tapped for Scope Mount
Sling Studs
Crossbolt Safety
Synthetic Stock and Forend
Non-Reflective Matte Black Finish
14" Length of Pull
Overall Length 46.5"
Weight 7.25 lbs
Includes:
Magazine Plug
Choke Tube Wrench
*****3 Flush RemChoke Tubes (Improved Cylinder, Modified, Full)