Connor is right that the Millenium foot-pockets will require socks. Any modular (interchangeable footpocket/blade) foot pocket system that I'm aware of should always be worn with at least a 1.5mm sock. If you dive in a cold place up to a 5mm, and if you dive where it's warm a 2mm is fine.
The reason you should wear socks is that while you might be okay for an hour or two without, any GOOD foopockets used in freediving fins will cause blisters and wear and tear on your feet otherwise. If they are so soft that you don't need a sock then you're wasting a ton of energy. The fact is that any fin that's 34-36" long if secured to your feet right will generate considerable strain on your feet if it's a powerful fin. Just ask anyone who has tried a one piece foot-pocket fin system and then switched to a modular system like Omer's. And also ask them if having to wear a sock to avoid blisters is reason to go back to a comfy fin that's not as efficient.
When I first started freediving the only two fins on the market were Sporasub and Cressi. Then, 20 years ago, Dessault's Sporasub footpocket was similar to the modern Sporasub pocket used up until today since they just discontinued production of them recently. The Cressi, Rondine Gara, was also a two piece system that had a replaceable grey blade much like Spora's. This is what everyone used since they were the best.
Well, to give you a bit of fast forward history they were both discontinued and replaced in favor of a more convenient and quick one piece production moulding. I loved the original Cressi footpocket, and for good reason, it must have been expensive to produce considering it used several rubber compounds to maximize comfort and power simultaneously.
Omer and a few other smaller companies then still sensing the market and demand by hard core spearfisherman for the two piece ones began selling their own version of replaceable foot-pocket systems. Omer's previous pocket was called the Tuna, same pocket used today by Biller, Spetton, C4, JBL and recently another American company picked it up for their new fin line. It was and still is today the only other molded separate footpocket available (made by an outside company) aside from Sporasub's and Omer's proprietary shoes. It is made from one rubber and only comes in three sizes, and as we remembered it, it was a horse shoe compared to then Sporasub's, and people always complained.
Omer in early 99-2000 developed the 5 molds of different sizes for the Millenium and whala', introduced the only multiple compound modular footpocket still available on the market today and that will be for years to come. Yes, more expensive to produce but the best and you can choose what blades and narrow down what size fits you with more choices than before. The Millenium puts a soft rubber in the neck of the foot, heel, and toes and a uses a stiffer rubber compound in the braces across the top, the sole and the ribs for the blade for efficient power transfer. A little bit of footpocket 101 since it's something I know a thing or two about
Probably more than you asked for and maybe you see why we we went through all this trouble..., you are a 40-42 based on what I read by the way.
Mark