No-Slip Hoops have a unique patented feature, a tongue and groove configuration, which holds the fabric securely between the inner and outer rings, thus keeping the fabric in place while working on the project. No-Slip means No-Slip - there is no movement of the project until the outer ring is loosened and the project is removed from the inner ring, which keeps your project taut while you are working on it! Size: 5". Made of plastic.