Shotgun shells come in various lengths, which are designed to accommodate different types of ammunition and shotgun chambers. The most common shotgun shell lengths are:

1. 2-3/4 inches: This is the standard length for most shotgun shells. It is compatible with shotguns chambered for 2-3/4 inch shells and is widely available for a variety of loads, including birdshot, buckshot, and slugs.

2. 3 inches: The 3-inch shotgun shell provides a slightly longer case, allowing for increased powder capacity and higher muzzle velocity. It is primarily used for more powerful loads, such as heavy hunting loads or magnum loads for increased range and stopping power. Shotguns chambered for 3-inch shells can also shoot 2-3/4 inch shells.

3. 3-1/2 inches: The 3-1/2 inch shotgun shell is the longest commonly available shell length. It offers the greatest powder capacity and is used for heavy magnum loads, especially for waterfowl and turkey hunting. Shotguns chambered for 3-1/2 inch shells can also fire shorter shells, such as 3 inches and 2-3/4 inches.

It's important to note that the length of the shotgun shell must match the chamber length of the shotgun for safe and proper functioning. Always consult your shotgun's manual or a knowledgeable professional to ensure you are using the correct ammunition for your specific firearm.