Hi guys. I'm building my second Fuji KR Concept rod and was wondering what are the factors that need to be considered in choosing the size of the running guides, now that we have more options. For my first KR rod I used 4.5mm running guides and it works great. For this 2nd rod, I intend pairing it with 3000 or 4000 reels having 15-20lb braid - I still want to build a micro rod for shore spinning but I want it to be a little bit tougher than the first one. Still don't know whether to raise the running guide size to 5mm or 5.5mm. Any idea on what I should consider for this decision ?

Generally the idea is to use the smallest and lightest guides that will easily pass your line, any connections, and hold up to the task required. If you need more strength for rough handling, etc., then larger guides might be in order. Then again, larger guides are easier to hang or catch on rod box lids, etc.

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Alistar;
I'm not sure what type of fishing you do. But I use braided lines between 65 to 80 test. Throwing Alabama rigs weighing up to 7 oz. on bait casting rods having ALPS 3-mm running guides all the time with NO problems.

On spinning rods I use braid up to 40 test with Batson's 2 and 2.5- mm guides that work great as well.

Alistar, the 4.5 runners will work just fine for a 3 0r 4000 series reel.. If you feel uncomfortable with the 4.5's you can go up to 5's, but it isn't necessary.. And that is using braid up to 20lb. test.

Agree with Ernest on size. Smallest line to line knot that is reliable is the Alberto, much smaller than the double uni. Just make sure to put the tag end back through the loop on the same side it came in on. If in doubt search for on-line knot instructions.

Alister,
If you have even a slight chance of running heavier mono line, consider the use of a bit larger guides.

Too be honest, I just do not know if fussing with these extra small guides is worth the hassle of putting them on a rod. But, do what you feel does the best job for you and your client, if building for a client.

Good luck

I don't think it's an issue of the line as much as it is of knots. 4.5's can take just about any line, but maybe not just about any knot.

Thanks for all your comments guys. Very helpful.