WTB Frequency TCS i23 Rim 32 hole Black 4D drilling provides a perfect interface between the rim and spoke and eliminates the need for eyelets I-Beam: a vertical beam designed to counter spoke loads and provide torsional rigidity Unbendium Bulge-a band of material added to the sidewall of the rim to counter torsional, radial and lateral flex Global Bead System (GBS) deeper grooves for the bead seats and two raised lips that lock the tire bead into place