Catch basin protection under the drain is nice. Its practical. Its useful. And, its out of the way and out of sight. But there are some reasons that above drain protection may be the better option. The Ultra-Filter Sock represents the ultimate in above drain protection. With the different filter media options available, this product is capable of removing many different types of pollutants. In fact, it is the only product with that versatility. The 9-foot long socks are placed in front of storm drains. The woven geotextile material allows water to flow through into the storm drain while the media inside of the unit removes pollutants.