With the headlight guard I have this bolt is used to secure the bottom of the guard and fairing to the lower triple clamp.
The stock sizes for my DR are:
Front: 90/90-21 54T TT
Rear: 120/90-17 64T TT
In my opinion, this is best used outside with a respirator.
Since the exhaust pipe has come out, I figure it's necessary to replace the gasket as well.
The exhaust header bolts. None of the Suzuki descriptions indicated the size. I picked the size up from a discussion forum. 8x25 seems right but I won't know until I try it.