Nice GWF62MAS picture! Is that the elastic natostrap from "cheapesnatostraps"?
Have the same and will show it here:

Johan it's the same pattern but not the same strap. Yours looks like a single pass, right?
The one send from Heimdallr is a marines type of strap. It's a "closed" strap, you need to remove the spring bars, place the strap, place back the spring bars and then adjust it using the metal hardware.