Amazon.com : High Definition 67mm CPL Circular Polarizing Filter for Canon EF 70–200mm USM Lens, Canon EF 70−300mm USM Lens, Canon EF 35mm f/2 is USM Lens & Canon EF 100mm f/2.8L
Canon DSLR Tip #5 - Why polarizer filter is a must | MicBergsma - YouTube