They resist flexing better than OEM rubber lines do, so they'll deflect less when under pressure. This improves overall pedal feel. Sometimes OEM rubber lines can cause your brake pedal to feel a bit soft or mushy if they're deflecting, and stainless lines will remedy this. They're not absolutely necessary, and the improvement in braking performance may not be that pronouced. Overall, I would think of stainless lines as one of the last brake system mods to do. Definitely get the pads first. Keep in mind that since stainless lines are more rigid, they won't be as flexible as the OEM rubber lines, which means if they're going thru a lot of suspension travel, like if you drive on VERY bumpy roads a lot(and the suspension is constantly compressing and rebounding its full stroke) the stainless lines may be more prone to failure. This is pretty rare, but there are isolated incidents of stainless lines failing when driven under these harsh conditions because they don't have the flexibility to sustain that kind of abuse. Under normal street/track duty, they should be fine. You probably wouldn't want to go rally-racing or off-roading with them, though