What Is the Difference Between Custom Windows and Standard Big-Box Store Windows? Custom windows are fabricated after taking exact measurements of your current window and wall opening. This ensures an accurate fit. Big-box store windows (those you can buy off the shelf) are an approximate fit and can lead to leaking, drafts, and premature wear and tear. In other words, . . .The post What Is the Difference Between Custom Windows and Standard Big-Box Store Windows? appeared first on Sunrise Windows & Doors.