Frost King R338H Marine-Grade Foam Weatherseal for Boat Hatches, RV Doors, and ATV Storage Boxes, 3/8" Black
Frost King R338H Marine-Grade Foam Weatherseal for Boat Hatches, RV Doors, and ATV Storage Boxes, 3/8" Black
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Why you'll love it
- Self-stick backing requires no tools, glue, or professional installation
- Wide range of sizes (11 variants from 3/16" to 9/16" thickness) ensures a fit for nearly any gap
- Rubber foam construction delivers both sealing compression and shock absorption in one product
- Multi-surface versatility works on home, auto, and marine applications from a single roll
- Made in USA manufacturing and limited lifetime warranty signal trusted, long-term quality
- Stretches slightly when laid in place to reach the actual advertised length
- Foam compresses nicely but is thick enough to not be crushed
- Adhesive remains strong even after 4+ years on previously purchased rolls
- Blocks drafts effectively even after a month of regular door opening/closing
- Easy to separate from backing paper
- Significantly dampens outside sound on casement windows
Perfect for
- Seal gaps around windows and exterior doors to block drafts and reduce energy bills
- Weatherstrip vehicle doors and trunks to cut down on road noise and rattles
- Weatherproof boat cabins and hatches against water intrusion in marine environments
- Cushion and stabilize appliances, electronics, or cabinet doors to prevent vibration
- Block dust, insects, and cold air from entering through small structural gaps
- Shimming a permanent A/C home filter that is slightly smaller than needed
- Replacing compromised weatherstrip on a 2005-2007 Mustang to fix water leaking onto floorboard
- Sealing lids on ATV/four-wheeler boxes to keep out moisture and dirt
- Preventing wind noise and air leaks around car windows
- Adding a cushion/protective strip that is sticky enough not to move
- Preventing rattling/noise on a window fan by taping where it contacts the window frame
- Sealing plexi panels over old windows without messy caulking
About us
From your basement to your roof, from the front door to the back, Frost King products are there to save you money and save you energy. Frost King, simply the trusted name in home insulation. It all began nearly a century ago when Frost King introduced the nation’s first do-it-yourself weatherstripping kit. That simple kit, just 17 feet of felt carpet strips and some nails, managed to single handedly ignite America’s “Do-It-Yourself” revolution. Since that time, Frost King has expanded to help you save money and energy in just about every corner of your home. During the winter, Frost King products will keep the cold air out, insulate your pipes and protect your rooftops from freezing snow. In the summer, Frost King keeps gutters clean, protects your home from leaks, and cuts air conditioning costs.
Frost King R338H Self-Stick Rubber Foam Weatherseal, 3/8"W, 3/16"T, Black|Blacks
A tough, durable self-stick tape with minimal compression. Use the Rubber Foam Weatherseal as a weatherstrip, or as a gasket or to cushion and stabilize major appliances. Plus, on cars, trucks and boats, it can help prevent rattles, vibrations and squeaks.
Product Information
The product is 3/8x3/16 BLK Foam Tape Easy and simple use kit The product is manufactured in United States Minimum Compression Superior Shock Absorbing Minimum Compression Superior Shock Absorbing Extra tough and durable Seals around windows and doors Many automotive and marine uses Show more
Brand Frost King Material Rubber Color black|Blacks Product Dimensions 120"L x 0.38"W Item Thickness 0.25 Inches Recommended Uses For Product weatherstripping, sealing gaps in vehicles, cushioning and stabilizing appliances UPC 077578012209 Number of Items 1 Manufacturer Frost King Unit Count 10.0 Feet Part Number R338H Item Weight 0.6 ounces Item model number R338H Is Discontinued By Manufacturer No Size 3/8"W, 3/16"T Style 3/8"W, 3/16"T Item Package Quantity 1 Included Components No Batteries Included? No Batteries Required? No Warranty Description Limited Lifetime Warranty
Frequently Asked Questions
Can I use this foam weatherseal on my boat hatch to keep water out?
Yes, the closed-cell rubber foam is marine-grade in its moisture and UV resistance, making it well suited for sealing boat hatches, marine cabin windows, and storage compartments against water intrusion.
Will the adhesive hold up in a marine environment with salt spray and sun exposure?
The closed-cell foam resists moisture and UV, and the pressure-sensitive adhesive is engineered for long-term bonding, so it performs reliably in saltwater and sun-exposed applications.
Does this work on RV slide outs that need a flexible, compressible seal?
Yes, the compressible foam structure is ideal for RV slide outs, RV doors, and RV windows, where it fills variable gaps and rebounds as the slide-out extends and retracts.
Can I use one roll for both my truck cab and my boat hatch?
Absolutely, the multi-surface versatility is a key feature — the same roll that seals your truck door panels can be used on boat hatches, ATV storage boxes, and trailer compartments.
Is the foam durable enough for outdoor storage box lids on an ATV or four-wheeler?
Yes, customers specifically use this product to seal lids on ATV boxes to keep out moisture and dirt, and the rubber foam stands up to vibration and trail use.
I'm a camper — will this work on my trailer or popup camper windows?
Yes, the self-stick foam is a portable, lightweight sealing solution that works on camper windows, trailer doors, and storage compartments without adding bulk or requiring tools.
Will it stick to the textured plastic on my RV exterior trim?
The pressure-sensitive adhesive bonds well to clean, smooth, and lightly textured surfaces including RV trim, fiberglass, painted metal, and plastic — just make sure the surface is clean and dry before applying.
Does this work in freezing temperatures on a snowmobile or ice fishing shelter?
The closed-cell rubber foam stays flexible in cold weather and does not absorb water, so it maintains its seal in freezing conditions common to outdoor and cold-weather use.
How does rubber foam compare to butyl tape for marine applications?
Butyl tape is excellent for permanent, high-pressure marine joints, but rubber foam is easier to install, removable, and ideal for hatches and cabin windows where you may need to access the seal for replacement.
Rubber foam vs. silicone bulb seal — which handles road vibration on a truck cab better?
The closed-cell rubber foam absorbs vibration and dampens rattles better than rigid silicone bulb seals, making it a strong choice for truck cab seals, door panels, and trunk lids.
Can I use this to weatherproof a rooftop cargo box on my SUV?
Yes, the self-stick foam seals rooftop cargo boxes, bike rack mounts, and accessory brackets against wind noise and water intrusion without drilling or permanent modifications.
Will rain and sun cause the adhesive to peel off my boat hatch within a season?
No, customers report the adhesive remains strong for years, and the UV- and moisture-resistant closed-cell foam is built to handle prolonged outdoor exposure.
Is this tough enough for off-road truck and Jeep applications?
Yes, the rubber foam withstands vibration, dust, and temperature swings typical of off-road and overland builds, and is commonly used on Jeeps, trucks, and 4x4s for sealing hard tops and door surrounds.
Will the foam absorb water and freeze in winter marine use?
Closed-cell foam does not absorb water, so it will not soak, freeze, or lose its sealing ability in cold, wet marine or outdoor environments.
Can I remove and reapply the foam if my sealing needs change seasonally?
While the adhesive is strong, the foam can be carefully removed and replaced with a fresh strip if your sealing configuration changes between summer and winter use.
Is the foam safe for use around outdoor food prep areas or picnic tables?
The closed-cell rubber is non-toxic and does not off-gas, making it safe for sealing coolers, outdoor kitchen lids, and picnic storage compartments where food contact is possible.
How do I install the Frost King R338H self-stick foam weatherseal?
Clean the surface where the foam will be applied, making sure it is dry and free of dust or grease. Cut the foam to the desired length with scissors, peel off the release liner, and press the adhesive side firmly into place along the gap. Hold for a few seconds to ensure a strong bond.
Can I cut the foam to size without fraying or losing the seal?
Yes, the closed-cell rubber foam cuts cleanly with scissors or a sharp utility knife, and the adhesive backing remains intact along the cut edge, so you can create custom lengths for any window, door, or compartment.
How long does the adhesive take to fully bond?
The pressure-sensitive adhesive grips immediately on contact, with full bond strength typically developing within 24 hours as it cures against the surface.
Will this foam stick to painted wood, metal, vinyl, and plastic surfaces?
Yes, the adhesive is engineered to bond to a wide range of surfaces including painted wood, aluminum, vinyl, plastic, fiberglass, and glass, making it suitable for home, automotive, and marine applications.
Is this product compatible with my 2005-2007 Mustang door seals?
Yes, customers specifically use this foam to replace compromised weatherstrip on 2005-2007 Mustangs to fix water leaking onto the floorboard, and it also works on many other vehicle door panels, trunk lids, and window frames.
What comes in the box when I order this product?
You receive one 10-foot roll of self-stick rubber foam weatherseal in a 3/8" width and 3/16" thickness, in black, with a release liner protecting the adhesive backing — no additional tools or accessories are required for installation.
Is rubber foam weatherstripping safe to use in homes with allergies or asthma?
Yes, the closed-cell rubber foam does not shed fibers like felt, does not absorb moisture that can harbor mold, and helps seal out dust, pollen, and outdoor allergens, making it a good choice for allergy and asthma sufferers.
Will the foam degrade or lose its seal if exposed to direct sunlight for years?
The closed-cell rubber foam is engineered with UV resistance to maintain its structure and sealing performance under prolonged sun exposure, making it suitable for both indoor and outdoor applications.
What is the difference between rubber foam weatherseal and silicone weatherstripping?
Rubber foam compresses easily to fill variable gaps, absorbs vibration, and is more affordable, while silicone weatherstripping offers higher temperature tolerance and longer UV life but costs more and is less forgiving on uneven surfaces.
