From viewing their very informative Web site, to working with my assigned representative Reed Nicholson - and then following their very well written measuring instructions (printed and video) using their supplied laser measuring equipment - I ultimately received exact fit Indow inserts for my kitchen bay window just before winter weather hit...and am now enjoying frost free windows above my kitchen sink area for the first time in years following a whole house window replacement project at which time I had triple pane windows installed everywhere but in the north facing kitchen bay window. Thankfully, Indow's innovation corrected this oversight on my part - just wished I would've done so much sooner!! And I see first hand why This Old House was so positive about Indow as well!!