Focus ST Track vent
99% are sold for aesthetics, however they are for the track. Some tracks require you to roll up your windows, this lets you vent with your window rolled up. It also reduces that helicopter pulsing effect you get when you lower the windows. It takes like 10 seconds to install.
The piece is made out of aluminum. You will need to bow it a little to get the curvature of the glass so it makes a good strong contact. The piece slides up into the window track, the window keeps it in place. For a tighter seal, you can use a door edge trim for $3 at pebpoys.
You get two panels.