I'm true to Samson's "true blue" 13.5 mm.,  Tuesday, 06 November 2007 I bought a 120' of Samson's "true blue" this Spring and have been using it this Summer and Fall for tree climbing and for safety on my roof. I like it's look and feel. It is very flexible. It works easily and it has held up well, though I am very careful to use a friction saver and to keep it clean. I'm not sure how to rate a rope for saftey but it certainly hasn't let me down.