Not sure about the 800 GS but the one on my 800ST and the GSA are the same. There are others you can use for 800 ST from.
Purolator PL 10241?PL25230
Supertech ST 3614
All these will fit ST You need the lower profile for the GSA due to the skid plate.
Hope this helps some anyways.
The reason for the different numbers is the washer that comes with them for the drain plug are different.
If you don't know where you're going
any road will get you there!
2009 BMW R1200GSA(Grey Boy)
2007 BMW F800ST(Blue Boy)