Cam tensioners as mentioned above. If the engine serial number has a dimple, or center-punch mark there, it has received the upgrade.
Several of the 'standard' top-end parts (including camchain tensioners) are no longer available ANYwhere. Good used seems to be the best folks can find.
The cams run in the bare aluminum of the head, and this can trash the whole head if it starves for oil. However, a zillion other Hondas and other mfg's followed this same philosophy without real troubles, so I tend to not worry about it.
Have fun with the job. I think the top end can come off without pulling the motor.
Kirk