I use these Mirka discs on a Porter Cable variable speed orbital sander. The hook and loop work well and the disc stays in place. I am a cabinetmaker as a hobby and work with cherry and walnut. The discs sand well and wear well. AS they lost their edge I have used them as finer sanding grits and they seem to do the job well.
Of course, nothing beats new paper for a job so if I need 150 grit, out comes a new disc.

If you have a Porter Cable sander with hoook and loop fastening this paper is for you. It is a cut above what you get from PC. It lasts longer and cuts faster from the start. Of course you will still have to change it to sand efficiently but not as often. At this price you can get several boxes in different grits and you'll be good to go for any sanding project.