Hair Thickening Fibers

SureThik hair thickening fibers make thinning hair look full in seconds. Each fiber is a micro-cut strand of keratin, sourced from premium wool and colored to match your hair.

They hold through wind, sweat, and light rain, then wash out with your next shampoo. Choose from 8 shades, or see exactly how hair fibers work.

What are hair building fibers and how do they work?

Hair building fibers are tiny colored strands of keratin or cotton that cling to your existing hair so it looks thicker. Human hair carries a natural negative charge, and the fibers carry a positive one, so they lock on electrostatically with no adhesive.

The fibers wrap each strand and fill in the contrast between hair and scalp. They need some natural hair to grip and don't treat hair loss.

Do hair building fibers have any side effects?

Side effects are rare. Fibers sit on the hair shaft, not in the follicle, and rinse out with shampoo. In a 2022 study of 40 people using keratin fibers for 90 days, no serious side effects were reported.

If you have a wool allergy or a sensitive scalp, try a small area first. Fibers also don't cause or contribute to hair loss. More in our guide to hair fiber side effects.

What are SureThik hair thickening fibers made out of?

SureThik hair fibers are made with just four ingredients: keratin from premium wool, sodium bicarbonate, silica, and iron oxide pigments for color. They're talc-free and sulfate-free, with no preservatives or synthetic dyes.

Keratin is the same protein your hair is made of, which is why it blends more naturally than cotton. See keratin vs cotton hair fibers to learn more.

How do I use SureThik hair thickening fibers?

• Style your hair and make sure it's completely dry. Damp hair makes fibers clump.
• Pick your shade, or go one shade darker if you're between two.
• Shake or pump fibers over thinning areas from a few inches away, lifting hair to expose the scalp.
• Pat gently to blend. Don't rub or comb through.
• Lock it in with Hair Fiber Holding Spray.

Learn more about how to apply hair fibers and how to choose the right color in our hair fiber colors guide.

How do I know if I need SureThik hair building fibers or hairline powder?

Use fibers for broad thinning where hair still grows, and hairline powder for edges and small, precise areas. Many people use both. 

See hair fibers vs hairline powder for more information.

How do I use SureThik Hair Fiber Holding Spray?

Apply it last, once fibers are in place and your hair is styled. Spray 2 to 4 pumps evenly over the area. You have about 15 seconds to adjust your style before the spray sets.

The alcohol-free formula dries to a light, flexible layer that shields the fiber bond from wind, sweat and light rain. Wash it out with regular shampoo, twice if needed.

How long do SureThik hair fibers last?

SureThik hair thickening fibers last until your next shampoo. With holding spray, they stay put through wind, sweat and light rain. 

With daily use, a 15g bottle lasts about 30 to 40 days and a 30g bottle about 60 to 80 days. More in how long hair fibers last and how to remove hair fibers.

Should I choose the 15g or 30g hair building fibers size?

Start with 15g if you're testing a shade or covering a small area. Choose 30g once you know your shade. It lasts twice as long and costs about 17% less per gram. If you are already a customer, you can stock up with one of our hair fiber kits.

Do I need the SureThik hair building fiber applicator tools?

No. The shaker bottle works on its own. The tools give you more control, which helps most at the hairline and part.

The patented pump applicator (U.S. Patent No. 11,511,312) attaches to the bottle and comes with three nozzle heads for concentrated or spread-out coverage. The hairline comb shields your forehead and sharpens edges. Buy the Applicator & Hairline Comb on its own or save with a 15g + Application Tools bundle.

How do SureThik's hair building fibers compare to other hair fiber brands?

SureThik uses precision-cut, micro-sized keratin fibers made from natural wool for the best adhesion. Compared to other top keratin brands, SureThik costs 12 to 20% less per gram and contains no preservatives.

SureThik also offers a patented three-nozzle pump applicator for more precise coverage. See the full side-by-side in best hair fibers: how the top brands compare.