These a great quality heated bed with a few extra features that you don't find on the more standard beds out there.
A small hole in the very centre allows a thermistor to come through and be in direct thermal contact with the print surface so you can get the most accurate readings possible.
3 mountin holes, perfect for delta-style printers.
Power Supply: 12VDC
Resistance: 3.5 Ohms
Printing area: 200mm MK2Y