I'm no IT expert, but if I understand correctly, the grading given is the maximum burn speed, not necessarily the only speed available. You may be able to instruct your device to burn at a slower speed than 24x. This should be set in your burning software when you come to burn the disc. However if you are unable to lower the speed to 16x on your machine I don't think you'll be able to use them.
Mark Dudley ● 5974d