I haven't seen them in real life - but they are tight on the models legs - so I'm guessing they will be fairly tight!
The Fly ones I have - are tight in the leg - but have a buckle on the outside - so can be lossened off a bit (which I need).
I have bought Oxygen boots before - they are almost identical - but in leather. The customer service was pretty dire when I had to return the boots - but they did say they had various 'technical' issues ie a fire - so they might be worth a try. The owner did sound a bit under pressure - but did get a full refund in the end. So he wasn't trying to rip anyone off - just not a slick operation iykwim.