Product review (5 stars): Love this!
I love this vent accessory!  I live in an apartment and was previously using an all-in-one portable washer/dryer unit (Malber WD1000) which drained the condensed dryer water into my kitchen sink and did not require venting.  The machine broke down and replacement parts are unavailable so after quite a few trips to the laundrymat, I purchased a portable washer and a compact portable tumble dryer but had no dryer vent hook-up.  The manual stated it needs to be vented outside or the warranty would be voided, so using an indoor dryer vent box wasn't the best option.  This aluminum window plate is the perfect solution!  It is very lightweight so it is easy to install and remove if you're unable to leave it in the window at all times.  It's made of a thin aluminum which isn't the best material against drafts, so if you are leaving it in your window permanently I would suggest using some insulation foam (like you would use for the sides of a window air conditioner) but otherwise I think it does an awesome job.  As one reviewer noted, it did have aluminum dust residue on it so I wiped it off before using it and it has been fine since.  I can't say enough about this product!  It has saved me from the dreaded trips to the laundrymat!