This is just a small alteration on the tudor/indoor riser blocks to make them more sturdy when stacked. They should fit all Magnetic or pin versions of the OpenForge bases and allow secure stacking without additional connections.

If you stick the Riser on a base itself, they seamlessly fit with other tiles and allow for infinite stackability :D The NoBase Variante is meant to be used without a base.and is therefore taller

They work/look really good with the balcony tiles https://www.thingiverse.com/thing:3590055 from Poxos