BECAUSE A GLASS MASTER IS WHAT IS USED FOR MAKING DUPLICATIONS OF CD'S. I DON'T KNOW MUCH ABOUT IT, BUT I SUSPECT IT RETAINS THE QUALITY OF THE MASTER CD AND DOESN'T SCRATCH AS READILY. WHEN YOU WANT TO ORDER MANY COPIES OF YOUR CD FROM A DUPLICATION COMPANY, I WOULD THINK THEY WILL DO IT AT HIGH SPEED WHICH WILL MAKE THE COPY NOT AS GOOD AS THE MASTER. MAYBE WITH A GLASS MASTER THIS WOULDN'T HAPPEN? ANYONE OUT THERE KNOW FOR SURE?