Cluster Density.

It isn't a huge revelation that grape bunches come in all shapes and sizes. From large well filled eating types to small tightly packed wine varieties.

These differences show up even before the flowers begin opening.

Here is Regent with long well spaced buds on the clusters. You just know these bunches will be loose, the grapes well spaced out.

Phoenix are much less loose but still not tightly packed.

Chardonnay form a pretty tight cluster but not so tight the individual grapes become deformed.

Brant clusters grow small tight bunches, the clusters reflect this.