If you click on the link, are all 1-3 feet at ten years old. I have Kashima, Kuro hime, and Bashful and can attest that they're very, very tiny:

http://www.davidsansjapanesemaples.com/japanese-maple-tree-selector/?winter_hardiness=zero&summer_hardiness=&tree_size=dwarf3&tree_form=&leaf_type=&spring_color=&summer_color=&fall_color=

very cool. Thank you

Also, you can prune them to stay small.

Yeah, but they don't stay that way :-) My Hupps Dwarf (which Davidsans says only gets to be about 1' after 10 years) is already about 3.5' tall and I've only had it a couple of years. It was already a decent size (at least 24" tall) when I got it. A great many JM's grow much faster than most folks expect and the mature sizes are only guestimates. My other dwarfs have already exceeded some listed sizes.

IMO, the best JM's to maintain at a very low height are weeping dissectums with a very low graft. Since they are not inclined to grow upright, they seldom put on much height. I am very hesitant to suggest to prune any JM to maintain a specific size. It's not really a good reason for pruning any kind of tree and JM's require minimal pruning anyway. Really just to thin the canopy a bit or enhance the growth habit. But I would not attempt to control size by pruning. Unless you are a very skilled pruner, the outcome will not be pretty.

Davidsans size projections are for zone 5b/6a. Up north many JMs stay smaller. I don't doubt that many get bigger than the 10-year size, but our growing conditions aren't the same as JM-ideal zones. Late Sound, what zone are you in?

I have a Ruby Lace that is only about 8" tall. It is about 24" wide from end to end but the nursery said it is 7 years old. It is a VERY slow growing cultivar.

I am in Houston TX, zone 9. I am thinking about getting 6~8 beni hime to put in flower beds in front of the house (3~4 on each side). I kind of fear that they will become too large overtime. I will google Ruby Lace to see that they look like. Thank you