High-Quality Vulcanized Rubber [Above OEM Grade]Bonded To Steel Outer Shell34.25mm OD x 11.5mm IDSold Individually - All Skunk2 products are carefully planned and designed in-house using the latest computer simulation and modeling techniques, followed by careful testing in controlled laboratory environments using state-of-the-art equipment. Each product is then subjected to rigorous dyno, street, and race track testing to ensure proper performance in the most extreme conditions. For these reasons, top street cars and race cars worldwide rely on Skunk2 products.