The dimensions 164 x 125 cm refer to the entire size of the mat including the sides but not including the bumper apron. The center area alone is 78 x 67 cm. The sides are reinforced with a bendable mesh wire so that they can be adjusted to your car's luggage space.
There is velcro on each corner and additionally, you can fasten the mat by placing straps around the back seat head rests.
Dimensions 164 x 125 cm
Maintenance note: Should the car seat cover be contaminated with saltwater after, say, a day at the beach, it should be immediately cleaned to avoid damage to the material.