Polylactic Acid Pen Machine Covers PLA (polylactic acid) is proposed of natural materials such as corn, cassava starch and has good biodegradable properties. Completely degradable by microorganisms in nature under specific conditions, and eventually generate carbon dioxide and water without polluting the environment. Main material: PLA Size: 60mm x 150mm 100pcs Suits best for Pen Machines from 25mm to 38mm diameter. Note: please store in dry, normal temperature environment, humidity and sun will accelerate the degradation time.