Rootstock: MM102 (apple)

Features:

• Size: Dwarfing (2.5m - 3.5m)
• Vigour: Medium (suitable for low vigour scions)
• Precociousness: Medium (occasionally fruits in second year after grafting, more commonly from the third year)
• Anchorage: Medium (requires staking for several years)
• Resistances: Highly resistant to woolly aphid
• Size of fruit: Normal
• Rate of graft failure: Low (6-8 weeks to heal)

Notes:

This rootstock is more balanced than an M27, adding some resistance to cold weather, and strong resistance to woolly aphids, while still maintaining a smaller size, and tolerance for being potted.
They anchor more strongly than M27 as well, requiring staking only for the first few years, and are more tolerant of drier conditions (though not "drought" tolerant).

They are not as precocious as M27, but are more vigorous, and as such are more suitable for less vigorous scions, and less suitable for highly vigorous scions (as they may over-grow, and under-fruit).

The fruit size is about what should be expected, not smaller or larger than the scions "seedling" fruit size, with no noted change to taste, or quality.

Conclusion:

They take a little longer to bear their first crop than an M27, but offer more resistances, and better anchorage, while remaining usefully small.
For a backyard/potted orchardist this is a great option!

However, due to the lower precocity vs M27, this is a poorer choice for home-scale breeding projects.
To that end I've personally used them only for grafting existing varieties that I'm hoping to use as parents, and later, as multi-variety trees, not for grafting test seedlings.