I was having some issues with PLA cooling and hardening on the edges of the nozzle. The cooled PLA would periodically break off onto the filament and cause the diameter to increase dramatically. These shrouds better direct the airflow from the cooling fans and help prevent from excessive cooling of the tip of the nozzle.
2x M3-35 or M3-40 socket head screws
2x M3 hex nuts
Ideally this should be printed in a material that can withstand high temperatures, like polycarbonate. In theory the shrouds shouldn't make contact with any hot parts or molten polymer, but better safe than sorry.