The Insert Double Hung is a complete new window unit used when higher performance or traditional interior aesthetics are desired or complete replacements are specified by your insurance adjuster. The frame of the ultimate BiltBest Insert Double Hung is placed inside the frame of your existing window. In comparison, the Tilt In Pack consists of replacement parts including an upper and lower sash, new Lowe Glass, new hardware and vinyl jamb liners for improved operation – all without disturbing the interior wall or exterior wall membranes – VERY IMPORTANT WITH STUCCO AND BRICK.