There really aren't any "great" outer sleeves for box sets on the market. They are either really loose bags, too thin (1.6 mil BOPP), have corners that stick out or made from foggy polyethylene.
Until now! I have developed a special crystal clear super strong 3 mil cast polypropylene (CPP) outer sleeve that has a square bottom. This sleeve is actually the same shape as the box set! Made from the same material as all of my other outer sleeves!
For closing the flap, I'd recommend using a small piece of soft release tape or you can purchase my resealable sticker (as shown in the picture) , once they are available.