I have the same as sleddog posted above. Even at 42" they are pretty heavy. Unless you have a specific need, I wouldn't put anything longer than 42" on a B series tractor. Perhaps, being a bit longer would make them easier to see (especially with painted tips)?
I use mine all the time as well. You'd be surprised at how well the do for moving brush. Also, I do use the built in receiver for moving trailers around. It works great and provides excellent control/maneuverability in positioning trailers.