I replied to another comment with the same question that I have never encountered this packaging. I get a cardboard box. Sometimes the blades inside are subdivided into little plastic capsules of five, sometimes they're just stacked in the box. But that slot is entirely new to me.

i just got these exact razors in the UK, but some blades such as Astras come in cardboard packaging

Those are my favorite blades

That sort of packaging is only on the blades that are more expensive than the blades the price conscious commenters have been quoting the cost of

Because the blades I get aren’t packaged this way. Is that a reusable outer package? I’ve never seen anything like that.