For a half-round window, a pre-curved trim sized to the opening is the most direct option. The FLEXTRIM casing choices cover different diameter ranges, while the FLEXTRIM brick molding offers a thicker, narrower profile. The moonoom self-adhesive molding is a flexible decorative alternative, but its listing does not specify a half-round size range. Measure the window carefully and match the product’s stated dimensions before choosing.
| Product | Best suited for | Stated size or profile |
|---|---|---|
| FLEXTRIM #445, larger range | Half-round windows from 42 to 56 inches | 11/16-inch thick, 3.25-inch wide |
| FLEXTRIM #445, smaller range | Half-round windows from 26 to 32 inches | 11/16-inch thick, 3.25-inch wide |
| FLEXTRIM #180 brick molding | Half-round arches from 34 to 40 inches | 1.25-inch thick, 2-inch wide |
| moonoom flexible molding | Decorative DIY trim projects | 20 feet long, 1.6 inches wide |
| FLEXTRIM #444 casing | Large half-round windows from 67 to 84 inches | 11/16-inch thick, 3.25-inch wide |
FLEXTRIM #445 Casing For 42–56-Inch Windows
This FLEXTRIM #445 casing is pre-curved for half-round arches measuring 42 to 56 inches in diameter. It is 11/16 inch thick and 3.25 inches wide. The listed features specify interior and exterior use and say the material will not warp, rot, or crack when exposed to high moisture. Installation is possible with normal woodworking tools.
Best for: Buyers whose half-round window falls within the 42-to-56-inch range and who want a wider casing profile. It was selected because its stated curve and size range directly address a common round-window trim need. Confirm the measurement method and opening dimensions before ordering; this size range will not suit windows outside its listed limits.
FLEXTRIM #445 Casing For 26–32-Inch Windows
This version of FLEXTRIM #445 is pre-curved for half-round windows from 26 to 32 inches in diameter. Its casing measures 11/16 inch thick by 3.25 inches wide. The product information describes it for interior and exterior use, notes resistance to warping, rot, and cracking in high-moisture exposure, and says it can be installed with normal woodworking tools.
Best for: Smaller half-round windows within the stated diameter range. Choose this option over the larger #445 when the measured window is 26 to 32 inches, rather than assuming the same casing fits every arch. Its size range is the main limitation: it is not listed for windows below 26 inches or above 32 inches.
FLEXTRIM #180 Brick Molding
FLEXTRIM #180 is pre-curved brick molding for half-round arches measuring 34 to 40 inches. The profile is 1.25 inches thick and 2 inches wide. Its listed diameter sizes match inner window jamb sizes. The manufacturer information describes it for interior and exterior use, including high-moisture exposure, and says normal woodworking tools can be used for installation.
Best for: Buyers seeking a brick-molding profile for a half-round arch in the 34-to-40-inch range. It provides a different width and thickness from the 3.25-inch-wide FLEXTRIM casing options. Important limitation: The listing says it will not fit eyebrow-type arches, so avoid it for an eyebrow-shaped window or an opening outside the specified range.
moonoom Self-Adhesive Flexible Molding
The moonoom trim is described as a 20-foot length of 1.6-inch-wide, self-adhesive, flexible 3D wall molding. The listing names walls, mirrors, window frames, and home decoration as possible uses. Unlike the FLEXTRIM products, the supplied details do not give a pre-curved half-round size range or state that it is intended for exterior use.
Best for: A DIY decorative project where flexible, adhesive-backed trim is preferred and the installer can shape it for the intended layout. It was selected as a general-purpose flexible window-frame option. Avoid choosing it as a ready-sized exterior arch kit when a pre-curved fit or stated moisture performance is required.
FLEXTRIM #444 Casing For 67–84-Inch Windows
FLEXTRIM #444 is the large-window casing choice in this selection. It is pre-curved for half-round arches from 67 to 84 inches in diameter and measures 11/16 inch thick by 3.25 inches wide. The listed details specify interior and exterior use and resistance to warping, rot, and cracking with high-moisture exposure.
Best for: A large half-round window that measures within the listed range and needs a 3.25-inch-wide casing profile. It was selected because the other pre-curved casing ranges do not extend as large. The product information does not list a fit outside 67 to 84 inches, so check dimensions rather than adapting this size by assumption.
Buying Guide: How To Choose Round Window Trim
How should you measure a half-round window?
Measure the window or jamb using the measurement method specified by the product listing. The FLEXTRIM #180 listing explicitly says its diameter sizes match inner window jamb sizes. Do not assume that the visible glass diameter, exterior frame, and inner jamb measurement are interchangeable. If the product details do not clarify the measurement reference, confirm it before purchasing.
Should you choose casing or brick molding?
Compare the profile dimensions and the look you need. The #445 and #444 casing options are 3.25 inches wide and 11/16 inch thick. The #180 brick molding is 2 inches wide and 1.25 inches thick. The listed features do not establish that these profiles are interchangeable, so choose according to the trim design and installation location.
When is flexible adhesive molding a better fit?
Self-adhesive flexible molding may suit a decorative DIY project where a set pre-curved diameter is not required. The moonoom listing gives its length and width but does not provide an arch-size range. For a half-round window needing a specified curve, the pre-curved FLEXTRIM products provide clearer sizing information.
What should you check for exterior installation?
The FLEXTRIM listings describe their products for interior and exterior use and mention high-moisture resistance. The provided moonoom details do not make the same claim. Confirm the intended exposure and installation requirements for your project instead of assuming all flexible trim is suitable outdoors.
Frequently Asked Questions
Which product fits a 30-inch half-round window?
The FLEXTRIM #445 listed for 26-to-32-inch half-round windows is the matching option, subject to confirming how the diameter should be measured.
Which option is listed for a 34-to-40-inch arch?
FLEXTRIM #180 brick molding is pre-curved for half-round arches in that range. Its listing says it will not fit eyebrow-type arches.
Is there a pre-curved option for a 70-inch half-round window?
FLEXTRIM #444 is listed for half-round arches from 67 to 84 inches, which includes a 70-inch measurement.
Can these products be used outdoors?
The FLEXTRIM product details state interior and exterior use. The supplied moonoom details do not specify exterior suitability.
Is the moonoom molding a size-matched round window kit?
The supplied listing describes flexible, self-adhesive decorative molding, but does not state a pre-curved shape or a round-window diameter range.