Good kit...BUT !
So ! I had the SACK MK3 for almost 6 months, my very first Spiritus product and it arrived on time but missing the shock cord, no biggie, i got em´ a week later, after that i use it in a more civilian role, i don´t carry a gun in it but i do carry a TQ, medical equipment, tools and other goodies, is just enough space for a compact IFAK, multi-tool, knife, power bank, and some other stuff to be more precise.
For the actual review, is a great simple design, i love the color choices, mine is grey for more of an urban role, it has a lot of modularity within, thanks to the big Velcro field, you can configure it as a med bad, as a tool bag, as an EDC fanny, it is the Lego of the fanny packs in that regard.
BUT, some of the stitching around the flaps that are fixed to the bag itself did stretch over time after some running and daily use, some frayed threads here and there, the materials is durable for what it is but it get kinda fuzzy with time and the strap could be better.
Overall, just buy it, is worth it...I would change to a thicker more durable material for heavier equipment, a thicker strap so is comfier when your wear it as an over the shoulder bag, more durable stitching and that´s it.