I don't buy into the sfs is so fragile mantra. I've never had a problem ripping the lace on those, I think they're quite strong. As far as them not lasting as long, my hair color would start to fade and get brassy way before the lace was used up, and then I would replace the unit so it didn't matter. Don't not get an sfs piece because you think it's too fragile, trust me. However, you will have the same knot issue with sfs (if they're not properly bleached). With i-lace you still need to have an sfs perimeter because the ilace is not good for hairlines, but for scalp appearance they are unbeatable. And again, same issues with knots on the sfs perimeter. i've had sfs hairlines completely exposed and it looked completely natural, no one could tell.