This ABS tactical helmet clamp adaptor is designed for cycling and hiking. It works with FAST helmet rails and allows for quick attachment or release from the rail system. The adaptor can be used to mount lights to the helmet, providing a convenient and secure way to carry your lighting. Specifications include a color that matches the picture, a quantity of 1PC, an outer diameter of 30mm, and an inner diameter of 25mm. The package includes 1PC helmet clamp adaptor. Please note that there may be slight differences in measurement due to manual measurement, and the color may vary slightly due to light irradiation or computer display differences.