One of the required items in the “Five C’s” is “cordage” but other than a passing recommendation to use 550 paracord that’s about where the recommendation stops. In recent weeks I had been testing 550 and 750 paracord, string, bankline, zing-it or catzeye.I’ll start with some of my troubles here.zing-it or catzeye is strong but just too slippery to use with prusik knotsbankline is terrible as a ridgeline because it stretches and the goop stains everythingstring does not handle water well and breaks easyby the time you put that sort of tension on a 750 knot the fibers melt making it difficult to untie550 is about 4mm in diameter and for all that weight and volume it’s normal uses are limited; granted the diameter makes it easy to handle and it is strong… but you’re not putting 550 pounds of pressure on a guy line.not included in the list is “Reflx; reflective guylines” from litesmith. It comes in 3 diameters including 1.1mm, 1.5mm, and 2.3mm. I now have 100ft of all three sizes.you have to look closely to see the size differences here as their distance from the lens varies enough to distort the relative sizes.the real size differencesWhat is great about this line is that it works well, is strong and holds a knot. 100ft of each of different sizes do not take much volume, they are strong, and highly reflective. Just look at the next picture.1.1mm Reflx - the reflection of light makes it appear thicker than it actually is. The only complaint that I might have with the 1.1mm line is that undoing a knot is painful or just difficult. I decided to use line-lok adjusters and they worked better than I expected… that and I also moved the stakes for more macro adjustments.I still like paracord, however, 80, 120, 275 are probably better for my needs. As for Reflx… I’m not trying to be stealthy so glow in the dark packs and cordage are OK with me.