Shot size refers to the size of the individual pellets contained in the shotgun shell. Common shot sizes include #8, #7.5, #6, and #4. The size of the shot can impact the pattern and penetration of the shot. Shotgun shells come in different lengths, such as 2 3/4 inches, 3 inches, and 3 1/2 inches. Longer shells typically have greater powder capacity and can provide more power to the shot.