What Does The "X" Mean When Choosing Leaders + Tippet?

Words + Photos By: Josh Thelin

What does the X mean? This is one of the most commonly confusing subjects within the fly shop. When choosing a spool of tippet or a pack of leaders, there are three main components of each: length, diameter, and poundage (breaking strength). 

For instance, Rio's Powerflex Plus 5X leader is listed as such: 

  • Length - 9'
  • Diameter (tippet) - .006"
  • Breaking Strength - 6lb

The system for the X is (supposed to be) universal. Every manufacturer's 5X should have a diameter of .006." The variable that is not universal is how these materials are manufactured to create these leaders or tippet. So you will see a wide range of "breaking strengths" with every manufacturer. For example Rio's Powerflex 9' 5X leader has a breaking strength of 5lbs where the corresponding Powerflex Plus leader has a breaking strength of 6lb. These leaders are machine tapered and the 5X is relative to the tippet section (end) of the leader. This is true for all leaders. If you see one labeled as a "5X tapered leader" the tippet section is 5X. 

What Does The X Mean In Choosing Leaders and Tippet?

Thankfully, the X does have a numerical value. That number is 11. So the math here is to find the diameter in thousandths of an inch. Take 11 and use it to subtract whatever the X value is to find the diameter. For example, to find the diameter of a 6X tippet, you would do 11-6 or .005" (aka 5 thousandths of an inch). 

The other criteria that you will see in the above chart is "suggested fly size." This is clearly suggested and has plenty of wiggle room, but tippet and flies seem to have a general balance that is recommended. This helps to give the fly and tippet combination appropriate movement depending on the fly and to also help create a better turnover of your leader. If you are looking to throw small dry flies, keeping in mind that a thinner and more malleable tippet will help drift those flies best and make your presentation as natural as possible will help you be more effective.  

I hope this helps the next time you are wondering what size tippet or leader to use! If you have any questions please feel free to email me: josh@allpointsflyfishing.com

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