PST thermal green film prevents weed growth like black plastic mulch while providing high enough soil temperatures for early productivity and plant growth, like clear plastic. While no mulching film can guarantee total inhibition of weed growth, this product will greatly reduce weed germination and weed growth due to its effect on photo-synthesis. Sun's radiation passes through the film, warming the soil. PST stands for Photo Selective Thermal. 1 mil plastic. Disregard product instructions where herbicide pre-treatment is recommended. Mulching film (mix or match) 5-9 rolls take 5% off; 10 rolls or more take 10% off.