The X marks the knot!
by Bill Byrd, Jr.

Do you understand the X system that has been in fly fishing forever? If someone says to you, "I'm changing to a 5X tippet," what does that person mean?

For a long number of years, manufacturers have used a simple rating system that describes both the diameter and breaking strength of tippet material. The basic scale runs from the heaviest 0X to the lightest 8X. Some have even gone so far as to suggest what size flies should be tied on what X value tippet. I'll equate all these values for you in this simple table.

X table with flies

X rating tippet diameter pound test suggested fly size
0X .011 inches 9.0 pounds size-4 to size-6
1X .010 inches 7.2 pounds size-4 to size-8
2X .009 inches 6.3 pounds size-4 to size-10
3X .008 inches 5.2 pounds size-6 to size-12
4X .007 inches 4.3 pounds size-6 to size-14
5X .006 inches 3.3 pounds size-14 to size-20
6X .005 inches 2.1 pounds size-18 to size-26
7X .004 inches 1.2 pounds size-20 to size-28
8X .003 inches 1.0 pounds * size-20 to size-28
● * is a fluorocarbon value.

These pound test and diameter values will vary from manufacturer to manufacturer, and with different materials. I have found the hard way that the real test value of some manufacturers leader and tippet materials may vary GREATLY from their labeled or published specifications. Be aware that all tippet values from all manufacturers can be certified by submitting samples to IGFA for testing.

NOTE: When fishing 4X to 8X tippets, you need to fully understand the role that your fly rod and reel play in fighting fish. If you don't fish a rod with the capability of protecting light tippets, you'll break off fish thus nullifying the purpose in using light tippets.