For 2-3/8" round gate frame Choose from 3" / 4" / 6-3/8" round post sizeIncludes heavy duty ABS cover to protect rollers and bearings in all weather conditions Includes strong magnets to help position the roller when mountingExtreme weather resistanceQuick mount magnetic base Galvanized metal components for long lasting performanceMachined 7" diameter nylon roller provides smooth operationFeature 1-1/8" axles and heavy duty bearingsHeavy duty ABS covers can be mounted on top or bottomSealed Bearings