Hello Nancy. Silhouette of any kind, needs at least 1" mounting depth to install it within the window frame. To fully recess the shade and headrail, 3" to 3 3/4" are required. Always keep in mind the window hardware. The back of the shade most clear any window handles, hinges by at least 1/4". If inside mount is not an option, outside mount is normally always possible. Window molding, casing ...etc needs to be checked to make sure the shade can clear them, and that the brackets can be mounted above, below or on them. I believe this answers your question. Please let me know if you need help with anything else.