What are the different sizes for oxygen cylinders?

Oxygen cylinders come in various sizes, commonly designated by letters. The most common sizes include the D cylinder (about 350 liters), E cylinder (approximately 680 liters), and K cylinder (around 6,800 liters). Larger cylinders, like the H or M cylinders, hold even more oxygen, typically over 6,000 liters. The choice of size depends on the intended use, such as for medical purposes, welding, or industrial applications.