Hi, I need to replace the spark plugs on my 52 uk WRX. The manual says NGK PFR6G but the NGK website says PFR6B. Is there a difference between the two and which would be the best to fit. The car is standard. Thanks for any advice.

 

PFR6B are fine, am sure everyone agrees. Not sure what the difference is tho'.
Am using PFR7's but car is running anything but standard....