I have been reading articles about finesse fishing and see that more and more fishermen are using 4# test. I have only used that light of line for trout and pan fish on ultra lite rods. Most of my spinning rods are rated for 8# or higher. I have a 6" med Fenwick Iron Hawk that is rated for 4# but I'm not sure it is long enough to fight Bass in the 3-4 # range.

Any info on what equipment is best would be appriciated.

Not a true #4 (.090" diameter, 8.5 lb test), but I caught these on #4 Yo-Zuri:

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As far as size goes, set your drag appropriately. I have caught numbers of 20+ lb drum and catfish on this line when smallmouth fishing.

8-)

I have been reading articles about finesse fishing and see that more and more fishermen are using 4# test. I have only used that light of line for trout and pan fish on ultra lite rods. Most of my spinning rods are rated for 8# or higher. I have a 6" med Fenwick Iron Hawk that is rated for 4# but I'm not sure it is long enough to fight Bass in the 3-4 # range.

Any info on what equipment is best would be appriciated.

No, a 6 inch rod really isn't long enough for Bass fishing.

Seriously, a 6' rod is just fine. It will work well with the line, and as long as it has enough "backbone" to move the fish, it will work. With 4lb test, your not really going to be fighting the fish too hard anyway's. The drag will be doing most of the work protecting the line and the rod. As long as there isn't much cover, you shouldn't have much of a problem.