This kit comes with 4 different sized Allen keys you need to clean and maintain your machine.
Comes with:
1x 1.5 mm Allen Key (Chrome)
1x 2 mm Ball End Allen Key (Black)
1x 3 mm Allen Key (Black)
1x T10 Torx Allen Key (Black)
The 1.5 mm Allen key is used for removing the mini fan that is in you laser head. Get behind all those crevices so you can remove dust that can fall onto the lense.
The 2 mm ball end Allen key is used for removing the main exhaust fan. Either to clean or to remove and replace with an external fan. The ball end is required to get at hard to reach bolts that you have to come at an angle. 
The 3 mm Allen key is used for replacing your belts and pulleys. The bolt that holds on the pulleys can be loosened in order to release tenision to remove the belt easy. Also need to remove the clamp bolts that keep the belts attatched to the gantry and carriage plate. 
The T10 Torx wrench is required to remove and clean the assist fan attached to the carriage plate and its vent for cleaning or replacing. The t10 can be used to pull apart your honeycomb tray for cleaning.