The 5671A is the number for non-projected tip.
The 5672A is the number for projected tip.

The heat ranges run from 5 to 11, hot to cold, and are closer together than most of the other plugs.

I've found with my 11 to 1 small block, I can get away with 8s on Drag Week, driving on pump gas, and then spraying at the track with 114 in the tank.

My brothers like to switch to a colder 9 or 10 when spraying their big blocks.

Plug Number/Part number
Projected tip
BCP6ES/4930
BCP7ES/5030
R5672A-8/7173
R5672A-9/7405
R5672A-10/7942

Non-projected tip
R5671A-7/4091
R5672A-8/4554
R5671A-9/5238
R5671A-10/5820
R5671A-11/6596

"Livin' in a powder keg and givin' off sparks" 4 Street cars, 5 Race engines