This is the MK31 Semi Variant of the Oshkosh Medium Tactical Vehicle Replacement or MTVR with an M970 fuel trailer.
The MTVR was introduced in 2005 and serves as a modular cargo truck platform with a variety of variants, this one being a semi truck.
The MK31 features a shorter frame than the MK23 variant, as well as 4 wheel steering for added mobility.
The M970 fuel trailer was introduced around 1980 and was designed for over and underwing refueling of aircraft. The trailer has a capacity of 5,000 US gallons.
This model features a functional fifth wheel capable of attatching and detatching the trailer at will without the use of magnets, a detailed interior with interior camera, functional doors, hatch, hood, and flap cap exhaust, a replica of a CAT C12 engine, independent suspension modeled off the real truck, a functinal tow hitch, and a detailed trailer complete with a ladder, pipes, pumps, hoses, and warning signs.

CONTROLS:

Pitch to drive.
Roll to steer.
Landing Gear operates the fifth wheel and trailer landing gear.
Act 1 and 2 operate the turn signals.
Act 3 activates a powerful gyroscope for righting the vehicle if it flips.
Act 4 opens the driver side door.
Act 5 opens the passenger side door.
Act 6 opens the hatch.
Act 7 opens the hood.
Act 8 toggles the running lights.
VTOL down opens up the trailer utilities.
TRIM down operates the rear tow hitch.

OPERATION:

To hitch the trailer, activate Landing Gear, reverse into the trailer, lining it up with the fifth wheel, once the trailer is in the fifth wheel, deactivate Landing Gear to close the fifth wheel and retract the trailer's landing gear. To remove the trailer, simply reactivate Landing Gear.

The MK23 variant

The MK25 variant

Just the Tractor

Just the Trailer