BR8ES (NGK)
UPDATE: As of January 2020, NGK has discontinued the B8ES and superseded with the BR8ES. The BR8ES is a resistor plug, which is designed to reduce electromagnetic interference of ignition systems for things like radios and phones while used in automotive applications. It is the new replacement plug for our vintage Honda motorcycles and performs just like the older B8ES spark plug. More info about resistor plugs can be found on the NGK FAQ page.
http://www.common-motor.com/honda-spark-plug-ngk