Measure the width of the opening from left jamb face (the deep pocket, not the face of the stop) straight across to the right jamb face. For units with jamb liners, you must first remove the jamb liners to reach access the jamb face. Measure at three three different points across the window and write down the smallest dimension.

Measure the height from the head jamb straight down to the point where the outside of the bottom sash touches the sill when closed (in line with the outside face of the sash). Check this height measurement at three points and write down the smallest dimension. Check that the angle of the slope of the sill is 14°.

Match these dimensions to Sun's standard sash kit size (see chart). If your opening width is up to 1/4" (maximum) larger than a standard size, you may shim behind the jamb liner clips to make the standard size fit your opening. If a standard width or height will not work, you will need to order your kits as Custom Size. Please provide your actual opening dimensions when ordering custom sizes.