You can find and purchase PDGA Approved discs, sold by major disc manufacturers, that weigh more than the PDGA rules allow. They don't have the excessive weight accurately marked on the disc, but if you weigh them, they are above legal weight. Also, it is possible that after purchase, a disc could gain weight by soaking in water, or accumulating dirt, etc. The rule stipulates 8.3 grams per centimeter of outside diameter. Are these discs illegal? Who is authorized to say? If I buy a disc that has a weight marked on it that is not accurate, and a TD says it is Illegal because it weighs too much, what do you do? The PDGA says "E. A player who carries an illegal disc during play shall receive two penalty throws, without a warning, if observed by two or more players of the group or an official. A player who repeatedly throws an illegal disc during the round may be subject to disqualification in accordance with 804.05 A (3). "