If you're asking about the DiNotte taillights, they do make a big difference. One of their greatest strengths is that you can be highly noticable from long range even in the daytime. One easy way to see the effect is to ride down the shoulder of a four-lane divided highway in daylight, and watch the semis in your helmet mirror. Turn the DiNotte on in flashing mode, and professional truck drivers will start changing to the left lane when they're still hundreds of meters back, if they can get an opening.