This is a blank brass disc that is about 50mm (+/- .01 mm) and .8mm thick.  I use these to prototype watch dials and also to make finished watch dials.  These do not have dial feet preinstalled so the material can be modified to thin the disk after engraving by milling the back, or sanding the back should a thinner dial be needed.  The .8mm x 50mm disc provides more material to help prevent heat deformation to produce a flat dial versus a thinner heat stressed engraving that is too warped to be used.  (Note: the thickness and size doesn’t eliminate heat deformation, but makes it easier to manager, especially when used in concert with a heat sink, like the Barger Watch 3-in-1 dial tool holder (sold separately, and a cooling fan or air assist.).   If you want to use the disc at full thickness you would want to use a high cannon movment (HC) such as the HH5 ETA, a GMT version of the Seiko NH (without installing the GMT hand)  or other high cannon movement. 
These blanks are sold for dial makers to use for laser engraving prototypes however, most are suitable to use to complete a finished dial. These are unfinished, and may require some preparation to complete a final dial engraving as they may have a small surface blemish (such as a light scuff or scratch due to rubbing during transit or during the manufacturing process. 
There are no dial feet preinstalled on these brass blanks and the positions for dial feet are not marked. For dial makers producing Seiko NH35 or ETA 2824-2 compatible dial foot dials the Barger Watch 3-in-1 Dial Tool can hold your workpiece dial securely while engraving and provide an easy dial foot template marking system to mark the dial foot location on these brass discs so you can precision place and weld, solder, or epoxy dial feet to the dial after engraving.