I just got these and they're perfect sizewise. There's no other size tags other than uk12 (probably Oki-Ni:s own tag) on the box and a 12 stamped inside the boot so I really can't tell what US(?) size they are. They're definitely larger than my UK11/US12 RW 875s so these will fit an insole no problem. I'd say these are pretty much similarly sized as the Timberland 6" premium boot in size US 12.
I'm happy to say I'm extremely (positively) overwhelmed by the quality of craftmanship put into these boots. The leather's

, the finishing is top notch and these look good as FxxK worn. I really hope these will hold up for a long time, I already have a couple of resole plans figured out over time

But first I'm going to start working on this bad ass wedge sole. Oh and did I say that I feel like a badass with these on...

More than happy with this purchase! And shipping took less than 48 hrs as well. Crazy.