Flex Shot vs Silicone Caulk. Which Is Better?

Until a few years ago, most people could only choose between polyurethane and silicone-based caulk. With the introduction of Flex Shot, there is a new caulking compound on the market that provides an alternative.

But what is this substance, how is it different than silicone, and which one should you use?
Man applying flex shot sealant instead of silicone caulk

What is Flex Shot?

Created by Flex Seal products, Flex Shot® is an adhesive sealant made from liquid rubber. Its reputation is that it has considerable bonding potential along with great flexibility. You can use Flex Shot for repairing, bonding, and sealing cracks or gaps in most types of material.

Temperature Range

Flex Shot Rubber Adhesive Sealant Caulk, 8-oz, Clear
Once cured, Flex Shot can withstand a temperature ranging from -76°F to 350°F (-60°C to 177°C). However, you must store it at room temperature to prevent the sealant from solidifying inside the tube.


A major advantage of FLEX SHOT is its ability to apply the seal without the need for any additional tool, such as a caulking gun. All you need to do is cut open the nozzle tip and push the nozzle towards one size. The sealant will come out of the tube uniformly, allowing you to apply it cleanly.

Available Colors

You can purchase Flex Shot in different types of colors such as clear, white, almond, and black.

Flex shot sealants
FLEX SEAL. Photo by: Colleen Michaels/Shutterstock.com

Advantages of Flex Shot

Since its introduction, Flex Shot has garnered a considerable reputation for its fast drying, flexibility, and consistency. When applied, Flex Shot will expand into the gap or crack, but never shrink once it has dried. Its rubbery properties mean that it is both waterproof and weatherproof.

For those who are considering Flex Shot, the main attribute is its flexibility. This means that you can keep it around the house and use it for a wide variety of surfaces and materials. When you need to create a seal that is still flexible, Flex Shot is the one for you.

In addition, the formula is quick-drying, so it can be applied easily and dried fast. The bond it forms is very strong, and you can use it on concrete, wood, and the like.


The downside is that Flex Shot does dry quickly and forms a considerable bond. This means that if you make a mistake, it is going to be difficult to remove the Flex Shot once it fully dries.

Another issue is that Flex Shot does have problems when exposed to heat and the ultraviolet or UV rays of the sun. Prolonged exposure means that the Flex Shot may deteriorate rather quickly.

Silicone Sealant

Silicone is a popular type of caulk that is often used to seal gaps and cracks in different types of material.

Based on a non-organic substance, silicone is generally superior to polyurethane-based caulk because it lasts far longer, creates a stronger waterproof bond, and can successfully resist UV rays.

Silicone caulking producing a uniform bead
Silicone caulk is typically clear or white, thick, and works in a wide temperature range. They can be used inside the house, bathroom, kitchen and on outdoor surfaces such as decks, patios, outdoor kitchens, porch, etc. They work well to seal cracks in damp areas and provide long-lasting protection against water damage.

Both FLEX SEAL and silicone can be used without a tool, but silicone caulk is applied better using manual or electric caulking gun.
So, how is Flex shot different when compared to silicone sealant?

Difference Between Flex Shot and Silicone Caulk

Flex Shot Silicone Caulk
Rubber based sealant Silicone sealant
Works on most surfaces, including wood Does not stick on wood
Acts as a sealant and adhesive Water-resistant and UV resistant
Can apply directly from the container Require caulking gun
Mainly for indoor use and on wood Used for both indoor and outdoor applications.
Silicone can be used both outdoors and indoors. However, it does have a couple of drawbacks.

Silicone does not bond well with wood. Plus, it does not adhere well to paint. So, if you are caulking a gap in wood that will be painted over, you should consider another type of caulk.

The main attributes of silicone are strength, versatility, weather and water resistance. You can use it both outdoors and indoors. Plus, it will last for a long time.

On the downside, you cannot paint over silicone sealant, it does not work well with wood, and it is generally more expensive.

Flex Shot is a rubber-based sealant and creates a much stronger bond when compared to silicone caulking. They also stick well on wood, paint, and most construction materials. The only condition is that the application surface should be thoroughly cleaned to remove any oil or grease.

Which One is Better?

Choosing between Flex Shot and silicone starts with the application itself. For areas exposed to UV rays or direct sunlight, moisture, and where the elements and surfaces do not need to be painted, silicone is generally the better choice.

For surfaces that are curved or uneven, Flex Shot may be better. For indoor jobs that involve wood or surfaces that will be painted, Flex Shot is generally superior to silicone. Flex Shot is somewhat more versatile compared to silicone, but in specific applications, you may want to use silicone instead.


Flex Seal Products is owned by Swift Response, LLC. They have several products, including seals, glue, tape, etc., and it can be confusing which one to use for your work.

Following are some of the common questions I get when working with caulk, flex shot, and silicone sealants.

Flex Shot vs Flex Seal, Are They Same?

Flex shot comes in a gel-like form, much like regular caulk, and is much thicker. Flex Seal is available in spray and liquid form.

Flex seal is lighter and can penetrate into very narrow gaps, while Flex shot is mainly used for filling large openings.

While both products cannot withstand extremely high pressure or temperatures, the Flex Shot and Flex Seal Liquid can survive temperatures up to 350°F, the spray is designed for a maximum of 140°F.

I would also avoid using the spray on porous stones such as granite, quartz, marble, etc, because it could potentially stain your stone countertop.

Is Flex Sealant Better than Caulking?

Again, it depends on the specific use. For indoor projects that involve wood, drywall, and will be painted, then acrylic-latex caulk and Flex Seal products tend to be better.

When it comes to filling large holes and gaps, you will want to use Flex Shot, as the thick rubber works better in such situations.

However, for outdoor use when the area will be exposed to the sun, then you will want to choose silicone sealant instead.

In terms of whether Flex Shot is better than polyurethane-based caulk, both appear to have similar attributes. However, Flex Shot may be a touch more versatile, and its rubbery qualities help it to last longer compared to polyurethane.

Can You Use Flex Seal Instead of Caulk?

For the Flex Seal spray, there are some instances in which you can use this product over caulk. For areas that need a temporary seal. Especially for a crack or gap that is so thin, applying caulk would not be practical, then Flex Seal can be used. However, Flex Seal is not as strong or as long-lasting as caulking.

In addition, you can apply a coat of Flex Seal over the Flex Shot. The Flex Seal will not adhere to the Flex Shot, but it will cover the surface and provide additional protection.