The largest mezuzah in the world was written by the scribe Rabbi Avraham Borshevsky. The parchment was 37 x 30 inches (94 x 76 cm) and was placed into a mezuzah case that was 3.6 feet (1.1 m) long. Each letter inside the mezuzah was 0.8 in. (2 cm) tall. The writing was of a very high quality (mehudar).
The Book of Amazing Facts and Feats #1: Largest Mezuzah