Reprap PCB Heatbed MK2 description:

• Dimensions 214 x 214mm
• 12V 200W
• Mounting holes 4x ø3mm. 2.5mm from the edge in each corner.
• Laminate FR4 1.6+-0.15mm 2 layer, Etched directly from 35um Copper and NO plating
• As the nature of the PCB material, flatness can't be defined and you will need an aluminum or glass top-plate.
• Resistance ~0.7ohm
• Black Soldermask top side
• Blue Soldermask bottom side
• White Silkscreen with ruler design - both sides
• Ready for through-hole/SMT resistor and LED (not included)
• ø2mm center hole for thermister mount

This is included in the Prusa Heatbed Mount Kit:

• 1 pcs Acrylic 5mm carriage plate 240 x 140mm
• 1 pcs Acrylic 5mm mount platform 240 x 225mm
• 4 pcs Springs
• 4 pcs Bulldog clips
• 8 pcs M3 x 25mm
• 20 pcs M3 nut