Getting ready to order a bit of fluorocarbon to use as a leader on some spiderwire stealth braid that I already have on hand. The spiderwire I have is 15lb. test, which equals 4lb. mono diameter. Wanted to get 6lb. fluorocarbon to use as a leader, but I'm not sure if I should go with 4lb. so the diameters match. Would prefer the 6lb. for the extra strength but don't want to compromise anything by using different diameter main line and leader. What say you guys?

I say you don't really need a leader at all. Why do you think you need one?

I use a leader on my spinning rigs in clear water.  In those cases I use 10lb with a 6 or 8lb leader.  So with that being said I think you will be ok with 6 or even 8lb.

I use 20lb braid with all sorts of leader size and never have any issues; all my knots hold just fine. I think it depends more on the presentation and what the structure is. Those 2 different line sizes are too close to have any affect on anything in that situation.

I, too, like a little more line strength so I would opt for the 6lb...or even heavier depending on what I'm doing.

What is the application anyway? What's the bait? What's the structure?

I use 12lb sunline sx1 main line with either a 6-8lb sunline sniper fc leader only in very clear water.

What is the application?

Thanks for the replies!! This is going on a new Pflueger President and either L, or ML 6'+ rod that I've yet to buy. This is going to be my go to, all around setup for smallmouth fishing the shallow, rocky and narrow upper Potomac river in Maryland. I'm thinking the braid with fluoro leader for things like tubes, worms, cranks etc. and then when I want to work some sort of topwater or maybe spinner I'll snip the leader and go with straight braid. Just trying to build a decent all around setup to avoid needing several different rod/reel/line combos on the boat.

I say you don't really need a leader at all. Why do you think you need one?

I've hauled in quite a few big largemouth with this particular line out of a calm clear quarry. The abrasion resistance wasn't the best so I figured when working bottom structure on the Potomac river the fluoro would hold up a bit better. The clearness of the fluoro also seems like a plus when slowly working a tube or something similar.

I think you're right on track. If you can't afford or just don't want 9  different rods in the boat, that's probably the best way to be universal. I'd go with the 6 or even 8 lb myself in that situation.

8 lb Seaguar Inviz is the same diameter as 15 lb Spiderwire (.009").