Blank CD-R mainly serve me in the manufacture of true audio CD. I'm half the tower (very late) and no defective CD-R. FYI, my first digital audio engravings from the mid 80's audio TDK are always spotless while some clones of Verbatim CD-R have failed. Very personal impression of a serious music lover who always low speed. The tower opens and closes with a screw, secure the quarter turn, I recommend.