These Race Face Single rings now feature performance-enhancing chain retention technology, allowing them (for most riders) to be used without a chainguide. The secret are alternating fat/skinny teeth to fit more closely into the narrow and wide plate spacing of a normal chain, "grabbing" the chain and holding it more securely... even without the use of a clutched derailleur.
The Narrow/Wide Single Rings are strong enough to stand up to the abuse of the downhill trail, yet light enough for cross country racers. Single Rings are machined from 7075 aluminum and tested in the most punishing terrain.