Originally Posted by LighthouseKeeper
Trio blocks are about a 1" cube, which I think is considered too small for toddlers. (At least, all the 1" cube manipulatives I've seen are rated for ages 3+.)

Just for future reference:

I went to a talk by a local child safety group. They said that a good rule of thumb is that if you can fit it through the inner cardboard tube of a roll of toilet paper, it is a chocking hazard for an under three year old. Might be handy to know if you are making your own manipulatives.