The SL920 Float Strap has 3.5 ounces / 100 grams of positive lift force in fresh water and 3.6 ounces / 103 grams of lift in salt water. This lift force calculation is at the surface only. The float strap is made of closed-cell soft neoprene so it becomes less buoyant at depth because the neoprene air cells compress with water pressure.
It is not the camera weight that determines if the strap will float the camera/housing or not. It is the weight of the camera in water that determines it’s buoyancy and required lift force. You can weigh your camera or housing in water using a fish scale or pull force gauge. If you weigh it in fresh water, add 3% lift force for salt water.
Please note: The attachment clip is for attaching to a vest or BC. Do not attach to the camera or housing.