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4 Lb. Density Expanding Pour Foam, 2 Part Polyurethane Closed Cell Liquid Foam for Boat and Dock Flotation, Soundproofing, Filling Voids, and Insulation (2 Gallon Kit)

Based on 498 reviews
Condition: New
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$114.99
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Availability: In Stock.
Fulfilled by Amazon

Arrives Sunday, Nov 1
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At a glance

Condition
New
Size
2 Gallon Kit
Model
poly4lb2gk
Material
Foam,Resin
Coverage
4 cu ft

Features 5

  • Flotation Foam is a polyurethane 2-part foam that, when mixed in equal parts and poured in place this foam will soundproof, insulate, or provide extra buoyancy.
  • 4LB. Density polyurethane flotation Foam 2 Gallon Kit; Consists of 1 gallon of Part A and 1 gallon of Part B and produces 4 cubic feet.
  • Once fully cured this foam can be laminated over with any type of polyester, epoxy or vinyl ester resin without melting.
  • The 4LB density also works well in floating decoy or taxidermy applications as well as many other sculpting, casting, carving and other filling applications.

Description

Fiberglass Supply Depot was founded in 2005, but our hands-on experience began in the Florida Keys in the 1980s, building boats, dock boxes and custom fiberglass products. We created FSD to give customers more than just materials—we wanted to share the knowledge to use them. Whether you're a professional or doing it yourself, we offer real-world experience to help you choose the right products and get the job done right. Our roots began in the Florida Keys in the 1980s, building boats, dock boxes and custom fiberglass products. In 2005, we turned that experience into Fiberglass Supply Depot. We don't just sell fiberglass supplies—we've actually used them. Our hands-on experience helps customers choose the right materials and understand how to use them. We enjoy helping people tackle projects themselves. From building to repairing and restoring, our goal is to provide the products and knowledge to help get the job done right. Quality materials backed by decades of hands-on experience to help you build, repair and restore with confidence.

Specs 12

Material Foam,Resin
Brand Fiberglass Supply Depot
Recommended Uses For Product Flotation, Soundproofing, Insulation, Filling Voids, Sculpting, Casting
Number of Packs 2
Manufacturer Fiberglass Supply Depot Inc.
Brand Name Fiberglass Supply Depot
Number of Items 2
UPC 819794022927

Frequently asked questions

If you place your order now, the estimated arrival date for this product is: Sunday, Nov 1

Yes, absolutely! You may return this product for a full refund within 30 days of receiving it.

To initiate a return, please visit our Returns Center.

View our full returns policy here.

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Top Amazon Reviews


You best be quick!
Size: Quart Kit
Good product but on a hot day it goes off QUICK! I used this to backfill fiberglass pool steps that were cracked. I learned on the first mix to not do a lot. The idea was to pour it into the holes I drilled into the stairs that would be patched after. Nope. I had about 3 seconds to get it into the hole as it started going off and most of it would up on the stair. I went out and got funnels for each hole, mixed for 10 seconds and removed the funnel fast. This was better. ... show more
Reviewed in the United States on June 7, 2026 by Matt W

Perfect
Size: Quart Kit
Works
Reviewed in the United States on August 12, 2026 by Amazon Customer

This is the best foam ever!!!
Size: 1/2 Gallon Kit
I used the 4 lb foam to make a custom dress form, it did well with a plaster cast you’ll want to paint the inside of the cast with latex paint and use mold release first. The foam is nice and dense! It sands well by hand or with an orbital sander. And it paints well too. You will NEED to use a mixing attachment for your drill!! I tried to mix by hand for a little batch and it did not foam up as much. You will also want to work within the temperature range. If you follow what it says to do it will expand 15x its size. I have bought this 3 times for 2 different custom projects and I will buy again! ... show more
Reviewed in the United States on January 19, 2026 by Devin

Be prepared.
Size: 1 Gallon Kit
It's it reacts very fast, especially when it's hot out. But it is very solid, takes about 10 minutes to set up completely. It works perfect for fence posts.
Reviewed in the United States on July 4, 2026 by marc s morante

Be mindful of temperature
Size: 2 Gallon Kit
I used this to repair some damage to a classic 13 Boston whaler. I actually redid the floor and have a word of advice for anyone new to this type of product. Prep your area well and understand the impact ambient temperature has on this foam. While liquid and while mixing/pouring this foam sticks to everything. EVERYTHING. I use masking tape and those cheap brown rolls of contractor paper to make sure the only thing exposed to the foam before and after expansion is the hole I’m pouring into. Regarding the temperature: the hotter it is outside the faster the foam mixes and needs to be poured. Also the hotter it is outside the more your foam will expand overall. I tried filling a small hole on a 70 degree day and the foam performed well. I thought….. the next week I filled a similar sized hole and used the same amount of foam. Only difference was the temperature outside was in the 90’s. I had the foam expand at least twice as far and ooze out all over the place. Just be mindful of them temp and as expensive as this foam is I suggest doing it on the hottest days you can so that you get the most expansion. ... show more
Reviewed in the United States on June 26, 2026 by Tcollins

Works well but sets very fast
Size: 1 Gallon Kit
It seriously sets way faster than expected, you get about 30 seconds of working time. I definitely don’t recommend mixing a full gallon at a time. But, it got the job done, my concrete slab is now level!
Reviewed in the United States on July 24, 2026 by Dustin Churchill

Fiberglass 4lb Density
Size: Quart Kit
as described and pictured
Reviewed in the United States on October 1, 2026 by TWINKLE

Mixes well
Size: Quart Kit
Works well. Use it for my taxidermy projects
Reviewed in the United States on August 19, 2026 by Todd hunt
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