This seat protector is intended to use to protect the seat of the car seat. It does not interfere in anyway with the buckles.
It is made of 3 layers.
Top is cotton knit print.
Middle is absorbent cotton fleece
Backing is waterproof PUL
The elastic casing in the middle is also lined with PUL and the elastic itself is tied lightly so can be adjusted to the fit you need.