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Frost King Window AC Side Panels vs Duck Brand Foam Window AC Insulating Panels

Both are two-panel foam side seals for a window air conditioner, and they are close to interchangeable. The Duck Brand has the far larger review base, 334 ratings against 21, so its 4.5 average is the more reliable signal. The Frost King is grey and self-adhesive; the Duck Brand is black and relies on friction and the window frame. Buy the one whose color and mounting suit your window, and check the panel size against your unit's side gap.

  • Choose the Frost King if you want a grey panel with self-adhesive backing that sticks to the unit or frame during install.
  • Choose the Duck Brand if you want the better-established panel with hundreds of owner ratings and a black finish that hides dirt.

Prices

  • Frost King Window AC Side Panels: $16.99 at The Home Depot (last seen Nov 10)
  • Duck Brand Foam Window AC Insulating Panels: $14.99 at Walmart (last seen Nov 10)
  • Difference: the Duck Brand Foam Window AC Insulating Panels is $2.00 cheaper than the Frost King Window AC Side Panels at the latest prices (Nov 10)
Frost King
Frost King flexible vinyl window air conditioner side

Frost King Window AC Side Panels

Frost King flexible vinyl window air conditioner side

4.5(21 ratings)
$16.99at The Home DepotChecked Nov 10
See all prices and details
Visit The Home Depot

Store links may earn us a commission. Price via Klarna.

Pros
  • Self-adhesive backing holds the panel in place while you close the window
  • Grey blends with light-colored frames and sills
  • Urethane foam is dense and cuts cleanly to size
  • Two panels cover both sides of one unit
Cons
  • Small review base, so durability reports are thin
  • Grey shows grime faster than black
  • Adhesive can leave residue if you reposition it
  • No stated R-value
Duck Brand
Duck Brand 18 Inch X 9 Inch X 0.88 Inch Black Foam Window Air Conditioner Insulating Panels, 2 Pack

Duck Brand Foam Window AC Insulating Panels

Duck Brand 18 Inch X 9 Inch X 0.88 Inch Black Foam Window Air Conditioner Insulating Panels, 2 Pack

4.5(334 ratings)
$14.99at WalmartChecked Nov 10
See all prices and details
Visit Walmart
Pros
  • Hundreds of owner ratings back the 4.5 average
  • Black hides dust and grime
  • Trims easily with a knife to fit odd gaps
  • Works with other Duck weatherization products
Cons
  • No adhesive, so it can shift before the window is closed
  • Stated R-value of 0, so it blocks drafts and noise more than heat
  • Foam can compress and lose seal over seasons
  • Black stands out against white frames

What separates them

Frost King Window AC Side PanelsDuck Brand Foam Window AC Insulating Panels
Panel size18 in x 9 in, 7/8 in thick18 in x 9 in, 0.88 in thick
ColorGreyBlack
MountingSelf-adhesive backingPress-fit foam, no adhesive stated
MaterialUrethane foamFoam
Owner ratings4.5 from 21 ratings4.5 from 334 ratings
Stated R-valueNot stated0
Pack count2 panels2 panels
Stated purposeReplacement side panels, noise and vibrationSealing gaps, dust, insects, pollen, noise

Price history

  • Frost King Window AC Side Panels: lowest $16.99 on Nov 10 at The Home Depot.

Prices at every store

Frost King Window AC Side Panels

  • The Home DepotNew

    In stock

    $16.99Checked Nov 10
    Visit The Home Depot
  • Lowe'sNew

    In stock

    $16.99Checked Nov 10
    Visit Lowe's
  • WalmartNew

    In stockSold by SIM Supply IncReturns: Sold by a Walmart Marketplace seller; returns go to the seller under the seller's returns policy.

    $26.39+ $5.99 shippingChecked Nov 10
    Visit Walmart

Store links may earn us a commission. Some prices via Klarna.

All 3 stores and price history →

Duck Brand Foam Window AC Insulating Panels

  • WalmartNew

    In stockSold by Guard Works LLCReturns: Sold by a Walmart Marketplace seller; returns go to the seller under the seller's returns policy.

    $14.99Checked Nov 10
    Visit Walmart
Prices and history →

Specs compared

SpecFrost King Window AC Side PanelsDuck Brand Foam Window AC Insulating Panels
ColorGreyBlack
MaterialUrethane FoamFoam
Panel dimensions18" x 9" x 7/8"—
Panel count2 Panels—
Overall height18 in—
Overall width9 in—
Thickness7/8 in—
FeaturesSelf-Adhesive—
Includes(2) Panels—
Protects againstNoise; Vibrations—
Compatible product typeWindow Air Conditioner—
size—18 in. x 9 in. x .88 in.
Show all 21 specsShow fewer specs
SpecFrost King Window AC Side PanelsDuck Brand Foam Window AC Insulating Panels
Panel length—18 in.
Panel width—9 in.
Insulation thickness—0.88 in
Panels per package—2 panels
Item weight—0.360 LB
Model number—287518
R-value—0
Weatherproofing kit type—Insulation Film
Number in pack—2

What reviewers say

Frost King Window AC Side Panels

  • 4.5 / 521 ratings

Buyers rate these panels well, mostly for sealing drafts and quieting older window units. Complaints center on fit and the adhesive letting go on some frames.

What people mention
  • Draft sealingPraisedOwners say the foam stops cold air leaking around the unit.
  • NoisePraisedSeveral mention the room is quieter with the panels in place.
  • FitMixedWorks well on standard windows but too small for wide openings.
  • AdhesiveCriticisedSome buyers report the backing peeling off after a few weeks.

Duck Brand Foam Window AC Insulating Panels

  • 4.5 / 5334 ratings

Buyers rate these panels well, mostly for filling side gaps quickly and cutting drafts and noise around window units. Complaints center on fit and durability rather than performance.

What people mention
  • FitMixedBuyers say the panels fit many window units but often need trimming, and some gaps are too large for the foam.
  • Draft sealingPraisedOwners report fewer drafts, dust and insects around the unit after installing the panels.
  • NoisePraisedReviewers say the foam dampens some AC vibration and outside noise.
  • DurabilityCriticised

Questions and answers

Which is better for blocking noise from the unit?
Both are thin foam and cut vibration and rattle more than airborne noise. The Frost King's adhesive keeps the panel tight against the frame, which helps slightly. Neither replaces a proper window seal.
Which lasts longer?
Expect a few seasons from either. The Duck Brand has far more owner feedback, and reports of sagging or crumbling are rare. The Frost King's adhesive is the first thing to fail if you remove and refit it.
Do I need adhesive to install these?
No. The Duck Brand panels stay put by friction once the window is lowered onto them. The Frost King's self-adhesive backing helps on units where the side gap is wide or the frame is uneven.
Will either fit my window air conditioner?
Both are 18 in x 9 in and about 7/8 in thick, the common side-gap size for standard window units. Measure your gap first; if it is wider, you will need to trim or double up.
Is the Duck Brand worth stepping up to over the Frost King?
They are the same size and material class, so there is no real step up. Pick the Duck Brand for its larger track record, or the Frost King if you want the adhesive and the grey color.

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More comparisons

  • Breeze Stop Surround Insulation for Window AC Units (Fits up to 36" wide window) vs Duck Brand 18 Inch X 9 Inch X 0.88 Inch Black Foam Window Air Conditioner Insulating Panels, 2 Pack
  • Frost King flexible vinyl window air conditioner side vs Breeze Stop Surround Insulation for Window AC Units (Fits up to 36" wide window)

Buying guides that pick them

  • Best insulated side panels for window air conditioners
Some buyers report the foam compressing, tearing or losing shape over time.