Not sure if it is made of Kevlar, but Sims improved them. The first sets I changed every other week..... but once I got the improved, and whether it is actually kevlar that is what the guy said. I use them for a year or so, then when I do maintenance on my bow I swap them out so they dont finally give out on a hunt. Junk? IMHO no but it all comes down to each his own. Personally, unless it is super pricey I like to try things for myself. Sort of like the movie everyone says you got to see and it is crap or vice versa. What I am saying, is the only way is to try it your self. And like everything else, you either like em and use em or hate em and don't. Me, as I have said many times, guys with brand new Matthews look at my 3 year old bow and ask what it is. When I say Matthews they look funny cause they say it is quieter then there new one with all the gizmos...... all I did was add some Sims stuff and yes, leeches and everyone just says they are amazed. Had a buddy 10 feet below say he couldnt even hear the release.... so are they crap? Maybe, but you know what, they will always be on my string........ [8D][8D][8D][8D]