About this item Comfortable Seating: The sofa seat cushion board provides a comfortable seating experience by providing firm support to the sofa cushions, preventing them from sagging and feeling lumpy.. Durable Material: Made of high-quality non-slip waterproof PVC shell and engineered wood,Extra Thick 1/3.5 Inch material,the sofa seat cushion board is sturdy and durable, providing long-lasting support for your sofa cushions.. Improved Posture: The sofa seat cushion board helps to improve your posture by providing better support to your back and hips, reducing the risk of back pain and discomfort.. Easy to Install: The sofa seat cushion board is easy to install and can be placed under the sofa cushions to provide additional support and firmness.The clever slat-like structure folds as needed to ensure flexible dimensions from armchairs to sofas. Just put it in according to your sofa size, the thicker and longer version can match your sofa more flexibly,fit any incremental width from 17"L to 22"W (fully extended)..