Thread: Different dimension for spark plug chambers?

I was looking to replace the spark plugs on my 99 Sentra SE-L yesterday and found that chambers 3 and 4 were of a different dimension from 1 and 2 I couldn't fit the socket I was using for 1 and 2 into the next corresponding chambers. Is this normal or do I have an issue here? Any help you might be able to provide would be awesome.