Fluorocarbon Fly Leader has a refractive index that is very close to that of water and as a result is very difficult to see underwater.
Leader material
Same refractive index as water
Quantity = 50m
Available sizes = 3lb (0.18mm/1.4kg), 4lb (0.20mm/1.8kg), 5lb (0.22mm/2.3kg), 6lb (0.24mm/2.7kg), 7lb (0.26mm/3.2kg), 8lb (0.28mm/3.6kg), 10lb (0.30mm/4.5kg), 12lb (0.32mm/5.5kg)