Bluestar Concrete Hairline Crack Filler is micron sized to penetrate and fill hairline cracks in concrete surfaces such as Driveways, Sidewalks, Patios, Steps, Garage and Basement Floors. This product is formulated to remain flexible, durable, and waterproof in hot and freezing temperatures. This product is formulated to flex with the expansion and contraction of concrete to resist cracking and leave an aesthetically pleasing appearance. 8 oz. size. See more