North Shore Billet Variable Tooth Chainring: 34T Shimano XT 8000 96 Asymmetric BCD Black. 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.