Our specially designed 4" knife-cut is best for fine and sandy soils. The perforations resemble a knife slit, just big enough for a piece of paper to enter but allows for minimization of infiltration from fine soils or sand. This type of material is a more cost-effective alternative to using the filter sock material and is used in many agricultural applications. This item requires freight charges which will be added at checkout. View list of freight costs based on your location.