Partnumbers starting with 91651 will be bolts with split washer + regular washer.
Then the second part gives the spec of the bolt, for example 91651-40845 is a long 45mm M8 :
4 => strengh
08 => M8
45 => 45mm long
I also ordered 91651-40825 recently for a shorter length.
In M6 you can find 91651-40616 for a classical 16mm M6 but a lot of other sizes are available, play with the partnumbers on a seller thats sells by partnumber.
Just 2 examples from 1 seller in Europe, but different availability from Amayama or Toyotapartsdeal.
As requested, here are some insights into understanding the Toyota part number logic for both legacy and current hardware. There is some back ground to understand though and some of it is easier to understand than other aspects: 1. Toyota part numbers are either 10-digits or 12-digits using a...