WE just took delivery of the two window inserts we ordered. they both fit perfectly. The most difficult part of the process was me trying to hold the laser measuring device still while taking the diaginal measurment! The Indow team was helpful and the ordering process was catch free. the finished product is just as they described. once installed, you can not even tell that they are there. I will warn you, if you have larger sizes they will come in a pretty large packing crate/box to protect them so be prepared. The only reason for 4 stars insted of 5 is they have just been istalled and we shall see how effective they are at reducing cold air, but they fit so snug that I anticipate they will be very effective. Just in time too, because our area is in a low temp/low wind chill pattern at the moment.