The HD Innovations UMS Round Rail Adapter gives anglers a secure way to mount sonar poles, fish finders, GPS units, and other marine electronics to round rails on boats, pontoons, kayaks, and custom fishing platforms. This HD round rail clamp fits 7/8 in. to 1 1/4 in. marine round mounting rails and uses soft rubber ring inserts with varying diameters to create a secure, protective fit. Crafted from high-quality 6061 T6 aluminum alloy, the clamp features CNC machining and a Type III hardcoat anodized surface for long-lasting strength and corrosion resistance in wet fishing environments. A TPU overmolded 1.5 in. ball head provides non-slip, wear-resistant performance and works with HD UMS system components, any 1.5 in. ball mounting components, and 1.5 in. ball double socket arms for adjustable rigging. Fits 7/8 in. to 1 1/4 in. marine round rails with included soft rubber ring inserts CNC-machined 6061 T6 aluminum alloy with Type III hardcoat anodizing provides strength and corrosion resistance TPU overmolded ball head offers non-slip, wear-resistant performance Compatible with HD UMS components, 1.5 in. ball mounts, and 1.5 in. ball double socket arms