Product review (1 stars): Flimsy and too short
Poorly designed product that can barely support itself when extended. Galvanized steel or thicker aluminum would make this a usable product.

Also, it was much too short to fit my window opening (46").

I ended up cutting a piece of 3/4" rigid foamboard (R4) to length and gluing 10" aluminum flashing to both long sides with gorilla glue. I then cut a 4.25" hole and installed a 4" dryer vent with silicone adhesive. 10x more sturdy and provides good insulation.