Direct from the PDGA:
"Discs must...have a flexibility rating no greater than 27 lb. (12.25 kg)...Flexibility - The disc is held on its edge in a vertical position perpendicular to a scale with a precision of at least 2 oz. (56.7 g). The upper rim of the disc is then gradually pressed down within 5 seconds. The flexibility rating is determined at one of two points, depending on how the disc reacts to applied pressure. For discs that buckle, the flexibility rating corresponds to the point when the maximum weight is registered on the scale. For discs that do not buckle, the rating refers to the weight at the point when the inside rim-to-rim distance is at 50 percent of the disc's diameter. The temperature of the disc is to be no higher than 25 degrees Celsius (77 F) when the test is performed. The ratings of three samples are determined, and the median score is used as the final rating. Discs that are unable to be bent to 50% of their diameters fail the flexibility test. Manufacturers are required to send samples of the most rigid discs they want considered for PDGA approval."
This disc takes 35lbs. Illegal!