To be completely honest, it's not the tape, it's how you paint. If you paint your base color over the tape before you paint the color you want, it won't bleed. For example, if you're painting the wall blue and don't want to paint the trim, tape off the trim but paint the area exposed where the trim meets the wall THE TRIM COLOR. Then, let it dry and paint the blue wall OVER the trim color. The base color will "seap" into the tape and leave a clean, straight line once you paint the wall color over it and then peel off the tape.