The Thermwell Products Co., Inc. 62 in. x 210 in. Polyurethane Extra-Large Shrink Window Insulation (2-Pack) helps improve the R-value of a single-pane window by up to 90%. The insulation features polyurethane construction.. Frost King window insulation kit for interior use. Energy saving efficiency to increase R-Values up to 90%. 2 sheets measuring 62 in. x 210 in.. Builders Hardware Product Type: Window Seal. Color/Finish: Clear. Interior/Exterior: Interior. Location Type: Windows. Material: Polyurethane. Product Height (in.): 62 in. Product Width (in.): 210 in. Unspooled Length (ft.): 18