The ServoCity 4.00" Foam Wheel (2 Pack) features a 16mm hole pattern, precisely measured across the center of the wheel, allowing for seamless integration with compatible hubs. These wheels are crafted from foam, ensuring a lightweight design with a total weight of 1.90 ounces. They are engineered to be adaptable with goBILDA® hubs through the use of specific adaptors and hardware, enhancing the surface area under the screws' heads for a secure fit. This product is ideal for applications requiring a balance of durability and lightweight performance.