Narrow, it's 75/250 so I only use it in the tranny. It's advertised and recommended right on the Baker website.
People may not approve but I've only changed my tranny fluid twice in over 42,000 miles on my Chopper. And on my 03 Mastiff I only changed it once with 24,000 miles on it. I guess since it's not exposed to fuel, exhaust and other impurities I let it go and even when I do drain it it comes out looking like new.
Good oil for a good tranny.
In the primary I use regular ole dinosaur oil 20/50. Either HD, revtech or whatever is available and this I do check often and change it out due to the clutch.
Later,
Ray