bluestar flexible concrete crack filler (light gray) bluestar two shades of gray - gray & light gray. the unique blend fills and seals cracks in concrete. this product is flexible therefore it flexes with the contraction and expansion of concrete. it also remains flexible in hot and cold temperatures. it is diy fast and easy to apply. no special tools required. seals to prevent further damage. 16 oz. size. also use to fill cracks on concrete steps, garage, and basement floors. made in usa.