I have the DROPRos magnetic scales on my lathe, here are the pro's and con's imo...
Pro's - Small and thin, about 1x.375 cross section. You can cut them to the exact size you need with any kind of metal cutting blade, hacksaw, chop saw, band saw. Impervious to coolant, chips, etc. Accurate, I'm holding within a few tenths on my lathe. I love the quality of the EL400, the display is really nice and cast aluminum not plastic.
Con's - The scale is flexible, pay NO attention to the leveling screws crap the scale needs to be mounted to a flat rigid surface. The scale will deform significantly (twist, bow) if the mounting surface is not flat. That's the catch, if say on the Z axis your mill column doesn't have a flat surface then you will have to mount the scale to some aluminum bar then mount that to the column so you just lost the small form factor advantage. On a mill mounting to the table which will be machined flat should not be a problem. I didn't machine the aluminum bar I mounted my lathe scale to e.g. it doesn't have to be absolutely flat, just flat within say .010. I did mount it to a thick ass bar, like 3/4 inch thick but keep in mind this was my lathe Z axis scale which was about 40 inches long. Also I found the chip covers for the kit pretty much useless, they are overly large. You could mill to size but frankly its probably easier just to purchase something closer to the correct size.
