Bubble Magic Extraction Terp Tubes are premium food grade stainless steel cylinders that are great for rosining your favorite herbal concentrate. Cut to size, fill with your favorite herbs/buds/flowers, fold ends and press. These 1''x9'' terp tubes can be cut down to any size that works best for you. What does micron sizes mean? The 25u offers smaller holes and gives you a more filtered and refined product where the 150u has larger holes that allows material to pass through easier and can potentially provide slightly higher yields.