mk3 heatbed mounting holes distance

hi all

please help me with the purchase of a heatbed.
i try to build a mk3 clone.
i had downloaded am made a frame and y carige from aluminium but i can not find an appropriate heatbed that can be installed on carrige / frog.
i had purchase a 220x220 heatbed with 214x214 mounting holes distances and does not fit.
what heatbed i need to buy for 210x215 holes, please see attachement. sorry for the poor quality
i need a standard heatbed? or is a custom one?

kind regards all

For those struggling to see your image..



The bed that sits on this is custom

mk52 heated bed by Prusa, also holds all the magnets for the steel bed. Also has the inbuilt fiducials (spots) that allow the firmware to detect them and adjust the XY for squareness

I see at least one company making clones of these beds...

Edited 5 time(s). Last edit at 04/28/2018 04:04AM by Dust.

thank you!!! very useful ! are you allowed to give me a link?
now i understand, i do not need magnets too advanced for what i need.
do you know a similar size bed? 12v preferably? and last if applicable similar mounting holes.

i had searched the web with no success.