I'm trying to figure out something. On TW I see two St. Croix rods. 

 

The first one is a 6'10" med lt. Line weight 6-10lbs and lure weight 1/8th to 1/2oz.

The 2nd one is a 6'10 medium. Line weight 6-12lbs and lure weight 1/8th to 5/16thoz. 

 

How is the first one a med lt and the lure weight is heavier than the 2nd? I know the 2nd handles 12lb line weight. Is the line weight the deciding factor?

 

Here is a case of a specialty rod design. The Medium rod was designed by the godfather of shakeyhead fishing so it is a brainchild of his. I have never touched the rod but unless a xhakeyhead rod is what you are looking for just look elsewhere in their lineup.

If you are looking for a good medium rod for finesse baits look at the St Croix Avid X 6'8 medium rod with an extra fast tip. I have had that one in my hand. i disagree with its extra fast label, more like mod fast but a terrific rod to throw Sencos, shakey heads, light texas rigs ans even tubes or grubs.  It rates for 3/16 to 5/8 baits.  Othewrwise look at a Powell, Dobyns or Irod.

Yup, the MF is for shakeyhead, tubes and craws on jigs. Also, I use the MF for swimming 3"-5" swimbaits. The MLF is more for hair jigs, sliders and smaller finesse stuff. I use the MLXF for casting and swimming grubs and smaller, lighter swimbaits.