Are N50 and N50B nozzles compatible with 808, 807 and 817 Handpieces?

Yes, both N50 and N50B nozzles are compatible as replacement nozzles for any tools that uses the 470 Series nozzles, ie: 808, 807, 817.  However, the 470 Series nozzles are not compatible for use with the FR-300 or new FR-301 Desoldering irons.