Tekton 7-Ball XT Ceramic Bearings with Patented High-Precision Built-In Spacer System. Next-level skate bearing tech – more speed, better handling, longer life! Ultra-Precise Alignment, 50% Stronger XT (Extra-Tough) Steel Casings, Tighter Assembly Tolerances, Dust-Resistant Ball Retainers, Premium Lube. Built-in half-spacers end in extra-wide contact surfaces (U.S. Pat. #9,126,101) that square up and self-stabilize inside wheels – correcting for flaws in bearing seat levelness, bearing seat spacing, axle diameter, and axle straightness. Combines with Tighter Radial Tolerances that minimize torsional play inside bearing assemblies. Locks in super-precise alignment, protects against friction and wear – better than any other system. Minimizes noise, too. Meets or exceeds all criteria for ABEC-9 rating.