Based on multiple regular and X-Lock disks, most of them should fit just fine. To be sure I added an additional 2mm tolerance to the 125mm spacing.
Dimensions: 3x3x6U
The model was made with OnShape and should be available to all https://cad.onshape.com/documents/d2b1533fdd4339235a0aeaef/w/dfd6302d8036a7602175fc06/e/4eada7cc2ac3b44c43933082
For some reason the viewer resets the Gridfinity settings so don't forget to set these (in the left top above the steps/features) to:
slotsDeep: 3
slotsWide: 3
slotHeight: 1
The author marked this model as their own original creation.