Here it is not legal any more to run a tractor without a R.O.P.S.
I have to pick one up for my old Fergie. It is basically a heavy round metal tube bent U shaped and plates welded onto the ends with bolt holes so you remove the rear wheel mud guard bolts, take of the guards, put on the R.O.P.S. then put on the mud guards and insert new (and longer) bolts.
$350 for one of these in
local currency, but I've seen up to $500 for less safe looking square steel tubes that have many pieces that bolt together making a somewhat U shape but all the weight is on those small bolts holding all the straight pieces together in a U-like shape.
Does not inspire confidence so I'm specifically getting an older-fashioned U shaped bent pipe R.O.P.S.
Cheers,
PeterD