The wr250r does not come stock with rim locks.
I have a extra set of wheels with michelin s12xc tires on them ( best tire off road for the wr that I found, and great in the sand )
Anyways on my last trail ride I was throttle raping the wr coming out of a corner and the wheel spun inside the tire causing the valve stem to shear off.
The tire went flat instantly and the back end was all over the place, luckily I was only going 20mph but if this happened at highway speeds the rider would be taking a trip to the pickers for sure.
I never realized how scary a instant flat can be without rim locks. They are not needed for stock tires on stock air pressure, but if you run knobbies at less then stock pressure get some rim locks.
The emgo ones are $8 shipped on ebay, I will never ride again without them