Knots; Perfection Loop

I like the perfection loop with heavy tippet of 20 lb or more. I have found, especially with fluorocarbon, that this knot will break relatively easily with lighter tippet. I think it has something to do with the way the knot tightens down causing a pinch in the line that creates a weak point. One thing that is very important is the tag end needs to be at 90 degrees when the knot is completed, if not it did not set properly and will fail. It's not the easiest knot to control the loop size, especially when used with a fly. A little adjusting as you tighten the knot will be needed to make sure the loop is not to large. However it is a popular knot for your leader butt while creating a loop to loop connection to your fly line. I also like using this knot on wire bite tippet, since wire is fairly expensive and this knot doesn't have a lot of waste.