The Oakley Flak 2. 0 Prizm Replacement Lens ensures that you always have the right tool for the job. Oakley's Prizm technology fine tunes vision for specific sports and environments, so you always have the optimal optics whether you're running, riding, or fishing. And with Oakley's interchangeable lens technology, swapping lenses is quick and easy so it won't slow you down. Proposition 65 Warning for California Consumers: This product contains chemicals known to the State of California to cause cancer and/or birth defects or other reproductive harm.