Welcome to the ForumSaludos! I am new to the forum, as well as van conversions. I recently purchased a 2016 Ford Transit 350 xlt with wrap around windows. There are 2 rear pop out windows that open a few inches.
If you are talking about the OEM windows behind the "B" pillar, they are not very well designed. Members reported them not staying open when moving, shattering for no reason. Multiple Threads on the topic, below is one.
Good Luck
Semper Fi

Broken Flip Out Windows
I now have two out of four flip out windows with broken plastic frames at the hinges. It looks like a design flaw due to the weight of the windows on the hinge while driving with them open. Add to that, two of them have leaked from day one, and I probably wouldn't recommend ordering this...