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💧 Seal it right, seal it tight — the pro’s choice for leak-proof peace of mind!
PROSOCO FastFlash is a professional-grade, fluid-applied flashing membrane that delivers a waterproof, airtight seal across a wide range of building materials. It cures in wet conditions, bonds without priming, and resists UV exposure for up to 12 months, ensuring durable protection against water and air infiltration in rough openings, joints, and seams.



| ASIN | B00OBUFLCW |
| Best Sellers Rank | #106,548 in Tools & Home Improvement ( See Top 100 in Tools & Home Improvement ) #48 in Roof Flashings |
| Brand | USASEALING |
| Brand Name | USASEALING |
| Color | Original version |
| Compatible Material | Alloy Steel |
| Container Type | Tube, Sausage |
| Customer Reviews | 4.8 out of 5 stars 253 Reviews |
| Item Form | Paste |
| Item Package Quantity | 1 |
| Item Weight | 16 ounces |
| Manufacturer | Prosoco |
| Material | Plastic |
| Material Type | Plastic |
| Model | 70400-SAUSAGE |
| Number of Pieces | 20 |
| Other Special Features of the Product | Solvent-free, isocyanate-free, phthalate-free |
| Part Number | PRS-70400-SAUSAGE |
| Special Feature | Solvent-free , isocyanate-free, phthalate-free |
| UPC | 653429020113 653429020168 |
| Unit Count | 20 Fluid Ounces |
| Volume | 20 fluid ounces |
| Water Resistance Level | Waterproof |
M**R
Easy to use, simple and effective - liquid flashing!
Prosoco R-Guard Fast Flash (and related Joint & Seam Filler) works as described to seal the gaps between different building materials. Tape and caulk products aren't all-purpose as liquid flashing products, where you apply a large bead in bulk, and then spread as needed for the situation. Corners, odd shapes, vertical, horizontal, works equally well inside tight spaces as it does across large flat areas. You can push the liquid flashing into cracks in the same way that caulk is applied, plus you spread it out with a plastic fin or other spreader tool. Cleans up easy with paper towels before it dries. The finished product is a rubberish mastic that provides a permanent barrier to water, air and insects. Cure (drying) time is dependent on humidity. If you're working in a very dry environment (e.g. below 50% humidity), a small amount of water misting with a spray bottle will speed things up. I'm in central Texas and find most days that I can spread the joint and seam filler in the morning, and then after lunch apply the fast flash. On especially dry days (humidity below 30%), I'll very lightly mist the substrate before applying the joint and seam filler. A great benefit, rain isn't a worry - you can apply these products and not worry about rain later in the day! The joint and seam filler is pink and reinforced with fibers, designed to fill large gaps between material, goes on very thick and the finished surface isn't as smooth/flat in comparison to the fast flash. Fast flash can be used by itself, or on top of the joint and seam filler. Dark red in color, nearly the same product as the joint and seam filler, but less fiber reinforcement to allow being applied as a thin top-coat that finishes smooth and sexy! Applied successfully at the foundation between concrete and base angle (e.g. sill plate) for metal buildings, workshops, and barndominiums. Works great for commercial and residential construction across a wide variety of materials!
K**N
Good stuff High price
This stuff is good. Easy to work with, but don't do a big area at once, it will tack up easy. Drys rock hard. My only downside is the price, one tube doesn't go very far. If you have a big budget or a small job this stuff works great. Big job small budget! You're going to be let down.
B**N
Seal with Confidence
The Prosoco R-Guard FastFlash Liquid Flashing Membrane exceeded my expectations in sealing and protecting my home. Its easy application and fast-curing formula make it ideal for sealing complex joints and penetrations. With its durable adhesion and flexibility, it provides reliable protection against water intrusion and air leaks. The 20oz sausage packaging is convenient and mess-free, making the application process a breeze. Whether you're a professional contractor or a DIY enthusiast, this product is a must-have for any construction project requiring top-notch waterproofing.
D**D
Amazing
Bond will last a lifetime. Probably the best product on the market Will tolerate weather changes and most movement if applied thick enough. Is not low cost Requires appropriate sized gun Difficult clean up. Once cured, it will take great effort to remove from any surface (not even a power washer will work) Red color not aesthetically pleasing for exposed work.
G**G
good stuff that does the job - but take time to mask off and cover the work area
this sealant is surprisingly easy to use and creates a thick and pliable seal around complicated forms. It does have a tendency to drip from overhead surfaces if it is put on too thick. Use the plastic spreader or a chip brush to smooth it out immediately. Use plastic drop cloths, wear gloves, and a work clothes that you don't mind ruining.
B**N
Stuff is great but expensive
Works, but a little spendy. Need to sell a 2, 3, 4 pack for cheaper or something
F**Y
Great for multiple substrates
Phenomenal product, sticks to everything, maintains its pliable rubbery qualities. Can’t imagine flashing an opening any other way. Air and water tight. Window flashing tape sticks like glue. It’s messy and sticky, if that’s a con it’s the only one I found.
S**B
Great stuff for sealing transition from sheathing to sill
I used this to seal the transition between OSB sheathing and sill plates that are sitting on concrete. It was easy enough to apply, although more liquid than expected. Once cured, it felt like rubber and it gives me confidence that it's a great seal. It took two sausages to cover 40 feet of sill plate.
Trustpilot
2 months ago
2 weeks ago