These chocks are unique because they are stackable. This feature really cuts down on the amount of space required to carry them in the plane. The durable plastic sides are lightweight, but are made to take a lot of abuse. There is space on the sides to put your airplane's N-number. The edges of these chocks are made of non-skid material, so they stay where you put them. They also won't damage anything else in your baggage compartment.