Must the disks participating to an ASM diskgroup of type normal-redundancy be of the same size ?

The bellow questions are triggered from an Exadata X2-2 configuration but is more ASM than Exadata related.

In Exadata the ASM disks are issued from the cellserver. Each cellserver provides access to celldisk (physical disks) which can be splitted into griddisks.
Griddisk are the visible as ASM disk to the ASM instance(s).

The partition of celldisk into griddisk can be done with hybrid size (eg 1 griddisk of 64G and another of 100G) as with consequence that the visible disk to ASM will be of different sizes.

Today nothing prevents an ASM disk group of type normal-redundancy to be build on (grid)disk of different sizes.