This 100% fluorocarbon tippet material from Rio is specifically designed for freshwater anglers seeking the ultimate stealth advantage. Because fluorocarbon possesses a refractive index very close to that of water, Fluoroflex becomes nearly invisible once submerged. This characteristic makes it exceptionally effective when targeting spooky fish in clear water conditions, whether presenting delicate dry flies, drifting nymphs through transparent runs, or fishing small emergers in flat water. The inherent properties of fluorocarbon also grant Fluoroflex superior abrasion resistance compared to traditional nylon tippets, providing confidence when fishing near underwater structure, sharp rocks, or sunken timber. Its higher density allows flies to sink subtly faster and helps cut through surface tension, which is beneficial for nymphing techniques and achieving a quicker, more natural drift beneath the surface. It maintains sufficient suppleness for reliable knot strength and smooth turnover, even with smaller diameter tippets. Size Chart0X: 0.011'' Diameter, 12 lb. Strength1X: 0.010'' Diameter, 11 lb. Strength2X: 0.009'' Diameter, 10 lb. Strength3X: 0.008'' Diameter, 6 lb. Strength4X: 0.007'' Diameter, 5 lb. Strength5X: 0.006'' Diameter, 4 lb. Strength | RIO Products Fluoroflex Freshwater Tippet Fishing Line | Size 4X