Even with a new central air unit the south-west upstairs bedroom was unbearably hot. I’m talking like 85* with the curtains closed. 
Our windows are the old type crank out and this fits perfectly. It works so well, I sometimes have to go up and turn the temperature back up to 72. Our grandson likes to set it on 65 and sleep with a blanket. 
I highly recommend this style unit for anyone with a small window. 
The only reason I didn’t give it five stars is because it’s a bit pricey compared to regular window AC units.