FELT DONUT BEHIND THE STEEL CRANK BALANCER
I figure its a good thing to keep dust away from your crank seal. Seems there might be more of a risk not using one than leaving it out.
If the factory put one in there then go for it if your balancer has the provision for it.
I was going to put one in my balancer only to find out it didn’t have the ring to hold the felt gasket.
Part #P5007301 I bought does not have the ring to hold the felt. Photo…
IMO I would use it.