Mark the location of underground sprinklers, pipes, and lines with 21 in. Red Marking Flags. These durable, long-lasting marking flags are constructed from weatherproof poly vinyl chloride that is designed with toughness to hold up to harsh outdoor conditions and maintain its shape. These marking flags are the perfect product for surveying, construction and agriculture. The marking flags are high visibility, fade resistant flags that easily mark communication, alarm, or signal lines. Get the job done right with these marking flags!