To measure Premium RV Day & Night Roller Shades with a 1.25" tube for an inside clip-in mount within valance boxes, start by measuring the inside width of the valance box at the top and subtract 0.5" to allow for clearance during installation. Next, measure from the inside top of the valance box to your desired upper stopping point of the shade when fully raised; a minimum of 5" is recommended for Duo Roller Shades. Then, measure the drop length from the inside top of the valance box down to the bottom of the window frame, ensuring at least 2" of extra space inside the valance box for the shade to roll freely. The final shade width tolerance is ±0.25". For mounting, use the simple metal clip designed for inside valance installation, available as an option when ordering. Note that Elkhart RV Parts provides shades from Irvine Shade ISD, the trusted premium RV shade brand. Following these steps will ensure a proper fit when replacing your motorized shades with manual cordless Slow-Rise™ roller shades.