Our Letterbox Tea Sachets Are Biodegradable - Here's Why That's Important June 25, 2021 We’re happy to share that our Letterbox Fine Tea sachets are made from a plant-based material called Polylactic Acid (PLA). This material is fully biodegradable (in high-heat compost conditions in about 2 months’ time), is not and has never been derived from plastic, is not petroleum-based, and is completely free from any plasticizers, glue, and metals. Read More