1.Plastic 2.Exceptional Durability and Anti - Slip Performance:Constructed from top - grade ABS+PC material, these grippers are extremely durable. Their anti - slip feature guarantees that your sheets remain firmly in position all night long, regardless of how thick your mattress is. 3.Effortless Installation and Reusability:Installation is a breeze! There's no need for any tools or complex procedures. Just slide the elastic straps into the slots, and you're done. These grippers are designed for repeated use, ing continuous convenience. 4.Universal Compatibility with All Mattress Sizes:Thanks to their expanded and widened design, including open corners, these grippers fit single, double, queen, and king - size beds perfectly. They effectively eliminate those unappealing gaps and wrinkles. 5.Highly Versatile and Multipurpose:These grippers are great for securely fastening fitted sheets, mattress pads, and waterproof covers. They are especially useful for busy families, parents, or anyone who is annoyed by loose sheets.