From the Rio website:
Powerflex Tippet – Guide Spool
High tenacity copolymer with excellent knot strength – ideal for trout.
- The RIO Powerflex Tippet Guide Spool is made from a a high tech co-polymer material, giving it excellent knot strength. A PTFE coating protects from abrasion, while giving it elongation (stretch) properties that average about 26%. Availabe from 7X to 0X, the Powerflex is perfect for all species. Its light grey color provides superb camouflage in the water.