I recently ordered a pretty large guide and tip top order from one of the sponsers.
During our conversations he stated that the minimum ring size for the tip top on a 9wt fly rod should be #6 or larger. What are your thoughts on minimum guide sizes for all fly rod weights? I always thought it just needed to be large enough to pass the knots.

Large enough to pass any required connections. That's about it.

I would suspect that he suggested a #6 or larger as most folks throwing a 9-weight would like to be able to pass some loop to loop connections on shooting heads or specialy leader connections. I normally use #8 guides and top on most of my heavier fly rods. If you don't specifically know what you're customer is going to be doing with the rod, it's better to go up a tad just to cover anything he might try to do with the rod down the road. No reason to go overboard - a #8 will handle most any decently tied or constructed connection you're likely to contend with.

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