Best way to mount this bag on Perun moto Top Luggage rack is to use Kriega OS-rack loops. These comes in two versions - OS-Rack loops and OS-Rack loops KTM fit. For this application, both will do. You will need to get the M6x20 button head bolts too, if you get the "standard" OS-Rack loops. Here is the needed hardware.
Install the rack loops on the underside of the rack, as shown on the photo. Use M6 button head bolts from above, and a small washer.
Here is OS-Rack loop, properly installed.
Rest is easy. Just use straps with G-hooks and attach them to the OS-Rack loops...
This bag has a bit larger footprint. To secure it properly, I suggest slightly modified mounting. Rear OS-rack loops can be kept, but at the front, use web loops which are delivered with the bag. Of course, if you don't have OS-Rack loops, web loops can be used at the rear too.
Web loops at the front.
Connect the G-hook straps to the web loops at the front and OS-rack loops (or web loops) at the rear.
Newest addition to the US Drypack line-up, quickly became one of my favorite bags. Capacity can vary from 20 to 40 liters. With the G-hook straps, provided with the bag, mounting to our Top luggage rack is very easy.
Just pull the G-hooks through the slots, as shown below.
And attach the bag, using G-hooks and quick-release buckles.
Due to the size of this bag, and some overhang at the sides, it is wise to put the heaviest content in the middle of the bag.
Again, perfect fit.
Final word. All these Kriega bags fit great and mounting system, with G-hooks and quick release buckles, is great. But, if the bags are empty, or only half full, bags won't fit perfectly - they will flap a bit. IMO, ease of mounting and quality of the bags make up for this minor annoyance.