Vinyl WHAT SIZE TO ORDER: This blind will be exactly 17.5 inches wide to ensure the perfect fit inside a window frame that is 18 inches wide. All Lumino blinds are precision-cut to be " narrower than the ordered width, providing the ideal inside mount. Please measure carefully see image with instructions to ensure the optimal fit. The sizes listed are WIDTH x HEIGHT. CUSTOMIZED IN THE USA: To ensure the perfect fit and a high-end look, Lumino cuts your blind to the exact size, right here in the USA. Unlike standard blinds that may come close, we ensure a perfect fit every time, so you won't need to compromise on size.