These are the heavy weight inner clamp rings and are machined from brass. Mix and match you inner rings to dial in that weight bias. They have a larger diameter bead lock ring, much like the Treal type B, smaller bead tires like J-Concepts and Pitbulls are a challenge to mount. If running Flubber Stufferz Slyme Ballz choose the T-type. Sold in pairs a full set requires two pairs.