Most rod, and reels coming out of the land of the rising technology are today rated with the PE system. Up until a few months ago this used to confuse the hell out of me, probably like many other people out there. Well, a bit of research here and a bit of chatting to some very knowledgable foreigners there and I got some explanations, which i thought i should share.
PE stands for PolyEthylene, the man made fibre that is used to make up the braided lines we use to fish and a whole bunch of other everyday materials. Lines usually come in 3, 6, 8, 12, or 16 strands, the more strands, the more it feels like silk (when un-coated), and generally the better it is i.e. more expensive. For example PowerPro, Spiderwire, Fireline are 4 strand lines. Dyneema or Spectra fibers are brand names of high-density poly-ethylene, the specific gravity is about 0.97 so it floats in water. Other hybrid lines may have heavier fibers which make them sink.
The PE measurement standard is based on a numbering system that was originally used to measure the thickness of Silk thread in Japan. The PE scale is constant and only reflects the thickness of the line and not the breaking strength. Line A and B could both be rated PE2 but, A could be 20lb line, and B could be 25lb, therefor the quality of the line must be considered. A very vague rule of thumb is to multiply the PE number by 10 to get the breaking strength. Ex: PE3 x 10 = 30lb, the line is rarely below that breaking strength but be careful it can very well be a lot higher!
Here is a table of equivalent diameters.
PE # Diameter
PE 0.6 ................................ 0.128mm
PE 0.8 ................................ 0.148mm
PE 1 ................................... 0.165mm
PE 1.2 ................................ 0.185mm
PE 1.5 ................................ 0.205mm
PE 1.7 ................................ 0.218mm
PE 2 ................................... 0.235mm
PE 2.5 ................................ 0.260mm
PE 3 ................................... 0.285mm
PE 3.5 ................................ 0.310mm
PE 4 ................................... 0.330mm
PE 5 ................................... 0.370mm
PE 6 ................................... 0.405mm
PE 7 ................................... 0.435mm
PE 8 ................................... 0.470mm
PE 10 ................................. 0.520mm
very interesting , thanks