The V-22’s interior presented unique challenges in that it was mainly designed for cargo and passengers, not vehicles. It is deemed too narrow for most vehicles.
The CH-53/MH-53 cannot fit a standard non-armored HMMWV inside as it is too narrow. The new USMC CH-53K can fit a HMMWV inside as it’s a bit wider. USSOCOM’s AFSOC no longer uses the MH-53 “Pave Lows” as these have been retired.
Thus started all sorts of vehicles to fit inside the V-22, such as the M1161 “Growler” and the Flyer 60. The problem with these very narrow (and sometimes very expensive) custom vehicles is that they might have a tendency to tip over as they’re pretty tall (I think the Flyer 60 (inches wide) is safe…doesn’t tip over…but I haven’t read or heard many soldiers use the Flyer 60; they use the Flyer 72 (inches wide)).
Enter ATVs, motorcycles, and dune buggies. Most of the dune buggies (such as the SEAL Desert Patrol Vehicle) lacks a radiator so they overheat in hot desert climates. And most ATVs and motorcycles seat one or two at best.
The MRZR is a militarized RZR ATV and you can see the radiator fan in the model kit through the front grill. It can seat four and still fit inside the V-22. A two-seat MRZR with trailer can fit inside a V-22.
The MRZR serves as logistics vehicle, weapons carrier, cargo carrier, recon, troop carrier, liaison, and transport to a whole host of equipment and weapons, including unmanned systems and anti-drone lasers. I haven’t heard or read of any tipping over. MRZRs cannot be purchased by civilians unless demilitarized.