Set of spacers for your Bosch Professional GKS 12V-26 (or GKS 10,8 V-LI, which is the same) and your Bosch Professional FSN guide rail (the new series, e.g. FSN 1100, which are identical to Mafell guide rails - you can identify them by their length in mm).
I just wanted to use the 12V Bosch GKS with my new FSN and realized that it isn't that easy to quickly mount it without the right distance to the splinter guard. Also I felt that one can hardly keep it parallel to the FSN guide rail, and some spacer would be desirable. Thus that thing.
With a brand new FSN without a damaged splinter guard I think I would start with the 13mm spacer at first, but you can pick the ones you like, especially if you already have a larger saw that changed the splinter guard's width.
To mount, just put it on with the printed width hidden by the black Bosch spacer - you‘ll sort it out ;)