Ardell Thick FX Medium Brown Hair Building Fiber for Fuller Hair Instantly, 0.42 oz The Solution For Thinning Hair Helps cover and color light to medium bald spots for both men and women! This Ardell Thick FX Medium Brown Hair Fiber is effective on fine hair and balding areas to make it appear thicker and fuller. It is also an excellent product to touch up gray areas of the hair and even out the color for a much younger appearance. Easy, Convenient, Instant Hair Loss Concealer Stays put and will make natural hair look thicker. Ardell Thick FX Medium Brown Hair Fiber easily hides small to medium size bald spots and grey hair.