My kids spend ages stacking these on the light table, and I've watched number recognition click for my four-year-old just from sorting the pieces by color. They're sturdy enough that my toddler hasn't cracked one yet, which says a lot.
Richard W.★★★★★
The color mixing is what really sold me — my four-year-old holds them over the light and watches the numbers change shade, which turned into a whole conversation about light. Nice size for small hands too, and they've survived being dropped on tile more than once.
Henry★★★★★
My toddler has been stacking these on the light table for a week and now she points out numbers on street signs. The translucent plastic glows nicely against the light panel, and they've held up fine to being tossed around.