MINIFOCUS 8 /20.3cm double ball adapter arm for underwater light system As a bridge to connect underwater tray/handle to underwater strobe/video light. Easy to assemble and disassemble, meeting various indoor/outdoor/underwater shooting needs, Waterproof & Rustproof. Specification: Material: Corrosion resistant anodized CNC aluminum alloy. Length: 8 /20.3 cm. (Length from the arm to the red ring.) Weight: 6.4 oz/181g. Ball size: 1"/25mm. Package Content: 1x 2" Double Ball mount arm 2x free replacement O-rings Upgrade your underwater photography with the buoyancy floating arm. Designed as an essential part of any scuba diving camera system, it serves as a light arm and balances the weight of your equipment underwater, reducing strain on your arms and wrists. To calculate the buoyancy needed for your camera system, determine the weight of your underwater set by using a hanging scale when it is submerged in water. Make sure to keep the scale above water as most models are not waterproof. Then, choose floating arms or floaters with sufficient positive floating capacity based on the weight of your set. Ensure that you have a balanced setup on both sides. Optimal number of mounting buoyancy blocks for MINIFOCUS 4" double ball aluminum alloy extension arm: 1pcs Optimal number of mounting buoyancy blocks for MINIFOCUS 5" double ball aluminum alloy extension arm: 2pcs Optimal number of mounting buoyancy blocks for MINIFOCUS 6" double ball aluminum alloy extension arm: 2pcs Optimal number of mounting buoyancy blocks for MINIFOCUS 8" double ball aluminum alloy extension arm: 3pc floating arm: outer diameter 8cm/3.2inch, thickness 3.8cm/1.5inch, inner diameter 2.5cm/1inch, provides 175g/6.2oz buoyancy. Package includes: 4x buoyancy arm blocks, 1x storage bag. The washers in the middle of the buoyancy block effectively secures the arm to your equipment and provides additional stability while diving.