J has a stainless top bar in the reel. Makes it a little stronger on the wider spool 300 series reels. The "J" stands for jig, as in, that is what you are throwing. The non-j, topless model is made for fishing live bait, which allows you to leave the reel in freespool and move the spool with your hand to take up slack and give line, without banging your knuckles into the top bar. California tactics.