The shimano xtr sm crm90 single chainring has been developed for heavy going aggressive trail use dynamic chain engagement technology creates a solid hold on the chain thanks to a broader and taller tooth profile in conjuction with a special hooked leading edge this allows the chainring to retain its firm hold even when riding over uneven terrain whilst running silently and keeping drag to a minimum shimano xtr sm crm90 single chainring features dynamic chain engagement dce hollow