The Kase K9 Lens Magnetic Lens Cap can be used to keep the Kase K9 adapter ring and 90mm CPL attached to your lens.
This cap is what you'll need to use if you wish to permanently attach the CPL to your lens as your original plastic lens cap will no longer fit.
This cap is NOT for use with the Wolverine magnetic or Skyeye magnetic circular filters - please check out the Wolverine magnetic cap options here.