correct, 40mm slots. Width is 21cm and height is 125cm. Both fairly arbitrary - was dependent on the wood I had to hand.
these are for kids shoes - for adults the slots would be slightly bigger - an adidas shell toe would fit, but a merrell doesnt quite - and it would need to be slightly wider.
At that price, I'd take at least 2 - it's not worth borrowing your design and making my own ...
What sort of dimensions did you work to? Something like 40mm slots?