Hero Sonic Xtra 215 is a Distance model disc, which has stickier plastic that allows you to grip it and throw, even with a disc coated in dog slobber. The smaller diameter is suitable for smaller dogs and for trainers who like the feel of a smaller disc. 215mm in diameter compared to a standard disc at 235mm. DISCLAIMER: These discs are NOT puncture resistant. Please purchase "Super" model discs for dogs with harder bites. Discs will not be replaced by damages incurred by dogs as these products are not chew toys.