Mine’s the jetstream II I think, £50 or so. A lot for a jersey, but I easily wore it 3x more than anything else last winter/spring. I bought it over the DHB version as the DHB was reviewed as having the windproof bits in the ‘wrong’ places (think it was lack of protection on the shoulders and forearms).
Just about everything front faceing is windproof, slightly thicker and tighter weeve than normal jersey material, the sides/armpits are more normal jersey material, the backs a kind of roubaix type material.
I had to go upto an XL otherwise it make a bit too much of a feature of my beer belly, if I can lose some blubber before this winter gets going propperly I’ll be treating myself to a new one in a saller size.