Features: Helmet mount carbon fiber extension arm, suitable for Hero 9 8 7 6 5 4 3, Max series/insta 360 One XR/Osmo/XiaoYi/EKEN/AKASO EK 7000 4K and more. Twill bright carbon fiber material, light weight, weighing only 20g, reducing the burden on the for head, comfortable grip, strong and durable, and not easy to scratch. Hollow design can greatly reduce the wind resistance during riding and improve the stability of shooting. Waterproof design, seawater corrosion resistance, not easy to seep water, can be used as a buoyancy arm, buoyancy coefficient: 5g. Widely used in outdoor sports such as skiing, skateboarding, cycling, motorcycles, parachuting, etc. (length: 98mm/164mm/25mm optional). Specifications: Material: Carbon Fiber Rod + Aluminum Alloy Tripod Adapter Mount Length: 257mm/164mm/98mm(Optional) Size 257mm: Approx. 257x105x10 mm/10.12x0.59x0.39 inch Size 164mm: Approx. 164x105x10 mm/6.46x0.59x0.39 inch Size 98mm: Approx. 98x105x10 mm/3.86x0.59x0.39 inch Package Includes: 1 Piece Carbon Fiber Extension Arm note: Please allow 0-1cm error due to manual measurement. pls make sure you do not mind before you order. Due to the difference between different monitors, the picture may not reflect the actual color of the item. Thank you!