The Counterweight for the Osmo Mobile is designed to offset the weight of the Iris Filter System. With the Counterweight, you can use the Iris, Osmo Mobile, and larger phones to capture smooth, cinematic content. The Counterweight is only needed when shooting with the Osmo mobile and the iPhone 6/7/8 Plus or Pixel 2XL. A rubberized coating was added to protect the finish on your gimbal, and a secure snap-on design allows you to quickly install and remove the Counterweight. Please select the counterweight you need according to the version of the Osmo Mobile you have.