Ruby Mac is on the small side of large, classically shaped with varying degrees of ribbing (one very ribbed, the other moderately so).
The dark red blush is a little dull and more even than that of many in the McIntosh family. Coverage is nearly complete, with just a few spots of light yellow-green peel where the sun didn't shine.
Tiny light lenticels are nearly invisible in the darkest regions of the blush, and the peel has a satiny finish.
A dusty bloom, patchy and thin, adds more visual interest. The apple itself is pretty firm in hand.
The flesh is more fine-grained than coarse and quite juicy, tinted green, and crisp though not hard. The flavors are balanced, though with some pleasing tartness, and present vinous flavors. There's also a little bit of raspberry, a nice touch, and some spice in the finish.
Ruby is clearly part of the Mac clan, distinguishing itself with some bright clean flavors. Note that the green-tinted flesh suggests my samples may be a bit early.
The seller describes Ruby Mac as a McIntosh x Rubinstar cross. But many other sources say that Ruby Mac is really a just sport of McIntosh, just as Rubinstar is a sport of Jonagold.
If so, its real name is "B. Thome McIntosh." More information in the 2006 patent.
Several other growers, on their web sites, take up the Rubinstar story, but I am tentatively persuaded by my tasting that "B. Thome" is most likely correct.
(Note, also, that "RubInstar, with an i, is not the same as recently reviewed RubEnstar, with an e. At least if the growers can be believed.)
It's not an infallible test, but Ruby tastes wholly of the McIntosh family, without a hint of Jonagold or its parents.