The NSB Variable Tooth Chainrings uses a ‘Thin-Thick’ variable tooth thickness mated with a standard chainring tooth profile to help retain the chain on the front ring during all types of riding. By increasing the tooth thickness on half of the ring’s teeth, the chain is given less room to move and virtually eliminates chain drop when running a single front chainring. Color: Black. Material: Aluminum. Chainring BCD: 64. Defined Color: Black. Ring Position/TYPE: Chain Retaining Single Ring. Drivetrain Speeds: 10. Drivetrain Speeds: 11. Tooth Count: 28.