Risers are designated by slot size.
For example a 1 x 1 x 1 is the smallest riser, fitting into a single slot deep, wide and the lowest height.
This would be 5.1cm deep, 10.8cm wide and 3.5cm high.
All risers can snap into each other like tiles, allowing you to mix and match your own display as you wish.
Size Breakdown:
1 wide = 10.8cm
2 wide = 21.6cm
3 wide = 32.4cm
1 deep = 5.1cm
2 deep = 10.2cm
3 deep = 15.3cm
4 deep = 20.4cm
1 high = 3.5cm
2 high = 7cm
3 high = 10.5cm