Adjustable screw-and-black-knob fixation system allows the cup holder tray to fit compatible bathtub edge thicknesses, with installation completed in just three simple steps. Note: This hot tub drink holder is not suitable for most pools, inflatable ground bathtubs, or drop-in bathtubs-verify your bathtub edge thickness fits the product's range before installation. Hot tub tray features a non-slip panel with drainage structure, paired with non-abrasive rubber grips to water buildup and keep the hot tub drink holder securely in place on bathtub edges. Made from storage board material, the gray cup holder tray long-lasting use without easy deformation, maintaining its shape and functionality over time. Dual large cup holders on the hot tub tray provide dedicated space for beverages, snacks, mobile phones, and other small items, catering to all your spa relaxation storage needs.