We have recommended two grit options in this belt size dependent on how aggressive you need to be:
If you are looking for a high cut, a long belt life and the finish is not important then the P40 grit belts will be ideal.
The P60 belts will also do a lot of material removal but with a little bit more control and if you are looking to do a further finishing stage afterwards then the P60 will almost certainly be the better option.